Real Estate Investments And Accumulated Depreciation (Schedule Of Real Estate Investments And Accumulated Depreciation) (Details)

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Real Estate Investments And Accumulated Depreciation (Schedule Of Real Estate Investments And Accumulated Depreciation) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Related Encumbrances		$ 1,403,615
Initial Costs, Land		789,095
Initial Costs, Building and Improvements		3,553,425
Costs Capitalized Subsequent to Acquisition	[1]	760,324
Gross Amount at Which Carried at Close of Period, Land	[2]	786,789
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,316,055
Total		5,102,844	[3]	$ 4,804,867	$ 4,807,718	$ 4,958,179
Accumulated Depreciation		1,087,083	[4]	$ 1,332,073	$ 1,464,482	$ 1,414,305
Real Estate Aggregate Cost, Tax Purpose		$ 3,900,000
Office [Member] | One Bridge Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1981
Acquired		1996
Initial Costs, Land		$ 2,439
Initial Costs, Building and Improvements		24,462
Costs Capitalized Subsequent to Acquisition	[1]	7,482
Gross Amount at Which Carried at Close of Period, Land	[2]	2,439
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	31,944
Total	[3]	34,383
Accumulated Depreciation	[4]	$ 16,885
Office [Member] | 2115 Linwood Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1981
Acquired		1998
Initial Costs, Land		$ 474
Initial Costs, Building and Improvements		4,419
Costs Capitalized Subsequent to Acquisition	[1]	7,756
Gross Amount at Which Carried at Close of Period, Land	[2]	474
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	12,175
Total	[3]	12,649
Accumulated Depreciation	[4]	$ 5,035
Office [Member] | 150 J.F. Kennedy Parkway [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1980
Acquired		1997
Initial Costs, Land		$ 12,606
Initial Costs, Building and Improvements		50,425
Costs Capitalized Subsequent to Acquisition	[1]	15,149
Gross Amount at Which Carried at Close of Period, Land	[2]	12,606
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	65,574
Total	[3]	78,180
Accumulated Depreciation	[4]	$ 30,833
Office [Member] | 75 Livingston Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1985
Acquired		2009
Related Encumbrances		$ 4,478
Initial Costs, Land		1,900
Initial Costs, Building and Improvements		6,312
Costs Capitalized Subsequent to Acquisition	[1]	(1,725)
Gross Amount at Which Carried at Close of Period, Land	[2]	1,281
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	5,206
Total	[3]	6,487
Accumulated Depreciation	[4]	$ 1,387
Office [Member] | 51 J.F. Kennedy Parkway [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1988
Acquired		2017
Related Encumbrances		$ 69,393
Initial Costs, Land		5,873
Initial Costs, Building and Improvements		100,359
Gross Amount at Which Carried at Close of Period, Land	[2]	5,873
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	100,359
Total	[3]	106,232
Accumulated Depreciation	[4]	$ 3,115
Office [Member] | 101 J.F. Kennedy Parkway [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1981
Acquired		2017
Related Encumbrances		$ 29,169
Initial Costs, Land		4,380
Initial Costs, Building and Improvements		59,730
Gross Amount at Which Carried at Close of Period, Land	[2]	4,380
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	59,730
Total	[3]	64,110
Accumulated Depreciation	[4]	$ 1,844
Office [Member] | 103 J.F. Kennedy Parkway [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1981
Acquired		2017
Related Encumbrances		$ 24,852
Initial Costs, Land		3,158
Initial Costs, Building and Improvements		50,813
Gross Amount at Which Carried at Close of Period, Land	[2]	3,158
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	50,813
Total	[3]	53,971
Accumulated Depreciation	[4]	$ 1,555
Office [Member] | 111 River Street [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2002
Acquired		2016
Initial Costs, Land		$ 204
Initial Costs, Building and Improvements		198,609
Costs Capitalized Subsequent to Acquisition	[1]	14,771
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	213,584
Total	[3]	213,584
Accumulated Depreciation	[4]	$ 8,680
Office [Member] | Harborside Plaza 1 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		1996
Initial Costs, Land		$ 3,923
Initial Costs, Building and Improvements		51,013
Costs Capitalized Subsequent to Acquisition	[1]	27,936
Gross Amount at Which Carried at Close of Period, Land	[2]	3,923
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	78,949
Total	[3]	82,872
Accumulated Depreciation	[4]	$ 44,931
Office [Member] | Harborside Plaza 2 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		1996
Initial Costs, Land		$ 17,655
Initial Costs, Building and Improvements		101,546
Costs Capitalized Subsequent to Acquisition	[1]	40,011
Gross Amount at Which Carried at Close of Period, Land	[2]	8,364
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	150,848
Total	[3]	159,212
Accumulated Depreciation	[4]	$ 64,754
Office [Member] | Harborside Plaza 3 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		1996
Initial Costs, Land		$ 17,655
Initial Costs, Building and Improvements		101,878
Costs Capitalized Subsequent to Acquisition	[1]	39,678
Gross Amount at Which Carried at Close of Period, Land	[2]	8,363
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	150,848
Total	[3]	159,211
Accumulated Depreciation	[4]	$ 64,754
Office [Member] | Harborside Plaza 4A [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2000
Acquired		2000
Initial Costs, Land		$ 1,244
Initial Costs, Building and Improvements		56,144
Costs Capitalized Subsequent to Acquisition	[1]	8,452
Gross Amount at Which Carried at Close of Period, Land	[2]	1,244
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	64,596
Total	[3]	65,840
Accumulated Depreciation	[4]	$ 29,121
Office [Member] | Harborside Plaza 5 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2002
Acquired		2002
Related Encumbrances		$ 209,180
Initial Costs, Land		6,218
Initial Costs, Building and Improvements		170,682
Costs Capitalized Subsequent to Acquisition	[1]	61,569
Gross Amount at Which Carried at Close of Period, Land	[2]	5,705
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	232,764
Total	[3]	238,469
Accumulated Depreciation	[4]	$ 98,606
Office [Member] | 101 Hudson Street [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1992
Acquired		2005
Related Encumbrances		$ 248,261
Initial Costs, Land		45,530
Initial Costs, Building and Improvements		271,376
Costs Capitalized Subsequent to Acquisition	[1]	16,952
Gross Amount at Which Carried at Close of Period, Land	[2]	45,530
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	288,328
Total	[3]	333,858
Accumulated Depreciation	[4]	$ 93,337
Office [Member] | 100 Avenue At Port Imperial [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2016
Acquired		2016
Initial Costs, Land		$ 350
Costs Capitalized Subsequent to Acquisition	[1]	4,205
Gross Amount at Which Carried at Close of Period, Land	[2]	471
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,084
Total	[3]	4,555
Accumulated Depreciation	[4]	$ 186
Office [Member] | 500 Avenue At Port Imperial [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2013
Acquired		2013
Related Encumbrances		$ 36,260
Initial Costs, Land		13,099
Initial Costs, Building and Improvements		56,669
Costs Capitalized Subsequent to Acquisition	[1]	(20,540)
Gross Amount at Which Carried at Close of Period, Land	[2]	13,099
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	36,129
Total	[3]	49,228
Accumulated Depreciation	[4]	$ 3,982
Office [Member] | 700 Horizon Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2007
Acquired		2007
Initial Costs, Land		$ 490
Initial Costs, Building and Improvements		43
Costs Capitalized Subsequent to Acquisition	[1]	16,663
Gross Amount at Which Carried at Close of Period, Land	[2]	865
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	16,331
Total	[3]	17,196
Accumulated Depreciation	[4]	$ 5,046
Office [Member] | 100 Overlook Center [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1988
Acquired		1997
Initial Costs, Land		$ 2,378
Initial Costs, Building and Improvements		21,754
Costs Capitalized Subsequent to Acquisition	[1]	4,245
Gross Amount at Which Carried at Close of Period, Land	[2]	2,378
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	25,999
Total	[3]	28,377
Accumulated Depreciation	[4]	$ 12,960
Office [Member] | 5 Vaughn Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1995
Initial Costs, Land		$ 657
Initial Costs, Building and Improvements		9,800
Costs Capitalized Subsequent to Acquisition	[1]	1,983
Gross Amount at Which Carried at Close of Period, Land	[2]	657
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	11,783
Total	[3]	12,440
Accumulated Depreciation	[4]	$ 6,547
Office [Member] | 333 Thornall Street [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1984
Acquired		2015
Initial Costs, Land		$ 5,542
Initial Costs, Building and Improvements		40,762
Costs Capitalized Subsequent to Acquisition	[1]	2,344
Gross Amount at Which Carried at Close of Period, Land	[2]	5,542
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	43,106
Total	[3]	48,648
Accumulated Depreciation	[4]	$ 3,319
Office [Member] | 343 Thornall Street [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1991
Acquired		2006
Initial Costs, Land		$ 6,027
Initial Costs, Building and Improvements		39,101
Costs Capitalized Subsequent to Acquisition	[1]	11,532
Gross Amount at Which Carried at Close of Period, Land	[2]	6,027
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	50,633
Total	[3]	56,660
Accumulated Depreciation	[4]	$ 14,840
Office [Member] | 101 Wood Avenue South [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		2016
Initial Costs, Land		$ 8,509
Initial Costs, Building and Improvements		72,738
Costs Capitalized Subsequent to Acquisition	[1]	692
Gross Amount at Which Carried at Close of Period, Land	[2]	7,384
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	74,555
Total	[3]	81,939
Accumulated Depreciation	[4]	$ 4,315
Office [Member] | 500 College Road East [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1984
Acquired	[5]	1998
Initial Costs, Land	[5]	$ 614
Initial Costs, Building and Improvements	[5]	20,626
Costs Capitalized Subsequent to Acquisition	[1],[5]	5,708
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	614
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	26,334
Total	[3],[5]	26,948
Accumulated Depreciation	[4],[5]	$ 13,152
Office [Member] | 581 Main Street [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1991
Acquired		1997
Initial Costs, Land		$ 3,237
Initial Costs, Building and Improvements		12,949
Costs Capitalized Subsequent to Acquisition	[1]	24,191
Gross Amount at Which Carried at Close of Period, Land	[2]	8,115
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	32,262
Total	[3]	40,377
Accumulated Depreciation	[4]	$ 15,056
Office [Member] | 23 Main Street [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1977
Acquired		2005
Related Encumbrances		$ 27,078
Initial Costs, Land		4,336
Initial Costs, Building and Improvements		19,544
Costs Capitalized Subsequent to Acquisition	[1]	13,944
Gross Amount at Which Carried at Close of Period, Land	[2]	4,336
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	33,488
Total	[3]	37,824
Accumulated Depreciation	[4]	$ 15,515
Office [Member] | One River Center, Building 1 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		2004
Related Encumbrances		$ 10,362
Initial Costs, Land		3,070
Initial Costs, Building and Improvements		17,414
Costs Capitalized Subsequent to Acquisition	[1]	11,421
Gross Amount at Which Carried at Close of Period, Land	[2]	2,451
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	29,454
Total	[3]	31,905
Accumulated Depreciation	[4]	$ 9,154
Office [Member] | One River Center, Building 2 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		2004
Related Encumbrances		$ 11,624
Initial Costs, Land		2,468
Initial Costs, Building and Improvements		15,043
Costs Capitalized Subsequent to Acquisition	[1]	4,101
Gross Amount at Which Carried at Close of Period, Land	[2]	2,452
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	19,160
Total	[3]	21,612
Accumulated Depreciation	[4]	$ 7,093
Office [Member] | One River Center, Building 3 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1984
Acquired		2004
Related Encumbrances		$ 18,472
Initial Costs, Land		4,051
Initial Costs, Building and Improvements		24,790
Costs Capitalized Subsequent to Acquisition	[1]	5,687
Gross Amount at Which Carried at Close of Period, Land	[2]	4,627
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	29,901
Total	[3]	34,528
Accumulated Depreciation	[4]	$ 10,588
Office [Member] | 3600 Route 66 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1989
Acquired		1995
Initial Costs, Land		$ 1,098
Initial Costs, Building and Improvements		18,146
Costs Capitalized Subsequent to Acquisition	[1]	11,471
Gross Amount at Which Carried at Close of Period, Land	[2]	1,098
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	29,617
Total	[3]	30,715
Accumulated Depreciation	[4]	$ 14,193
Office [Member] | 100 Schultz Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1989
Acquired		2017
Costs Capitalized Subsequent to Acquisition	[1]	$ 8,743
Gross Amount at Which Carried at Close of Period, Land	[2]	1,953
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	6,790
Total	[3]	8,743
Accumulated Depreciation	[4]	$ 556
Office [Member] | 200 Schultz Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1989
Acquired		2017
Costs Capitalized Subsequent to Acquisition	[1]	$ 10,443
Gross Amount at Which Carried at Close of Period, Land	[2]	2,184
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	8,259
Total	[3]	10,443
Accumulated Depreciation	[4]	$ 495
Office [Member] | 325 Columbia Parkway [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1994
Initial Costs, Land		$ 1,564
Costs Capitalized Subsequent to Acquisition	[1]	18,368
Gross Amount at Which Carried at Close of Period, Land	[2]	1,564
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	18,368
Total	[3]	19,932
Accumulated Depreciation	[4]	$ 12,583
Office [Member] | 1 Giralda Farms [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1982
Acquired		2017
Costs Capitalized Subsequent to Acquisition	[1]	$ 30,515
Gross Amount at Which Carried at Close of Period, Land	[2]	3,370
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	27,145
Total	[3]	30,515
Accumulated Depreciation	[4]	$ 1,014
Office [Member] | 7 Giralda Farms [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1997
Acquired		2017
Costs Capitalized Subsequent to Acquisition	[1]	$ 43,066
Gross Amount at Which Carried at Close of Period, Land	[2]	5,402
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	37,664
Total	[3]	43,066
Accumulated Depreciation	[4]	$ 1,246
Office [Member] | 201 Littleton Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1979
Acquired		1997
Initial Costs, Land		$ 2,407
Initial Costs, Building and Improvements		9,627
Costs Capitalized Subsequent to Acquisition	[1]	3,132
Gross Amount at Which Carried at Close of Period, Land	[2]	2,407
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	12,759
Total	[3]	15,166
Accumulated Depreciation	[4]	$ 6,416
Office [Member] | 4 Campus Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		2001
Initial Costs, Land		$ 5,213
Initial Costs, Building and Improvements		20,984
Costs Capitalized Subsequent to Acquisition	[1]	4,117
Gross Amount at Which Carried at Close of Period, Land	[2]	5,213
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	25,101
Total	[3]	30,314
Accumulated Depreciation	[4]	$ 10,513
Office [Member] | 6 Campus Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		2001
Initial Costs, Land		$ 4,411
Initial Costs, Building and Improvements		17,796
Costs Capitalized Subsequent to Acquisition	[1]	3,550
Gross Amount at Which Carried at Close of Period, Land	[2]	4,411
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	21,346
Total	[3]	25,757
Accumulated Depreciation	[4]	$ 9,177
Office [Member] | 7 Campus Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1982
Acquired		1998
Initial Costs, Land		$ 1,932
Initial Costs, Building and Improvements		27,788
Costs Capitalized Subsequent to Acquisition	[1]	6,573
Gross Amount at Which Carried at Close of Period, Land	[2]	1,932
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	34,361
Total	[3]	36,293
Accumulated Depreciation	[4]	$ 17,234
Office [Member] | 8 Campus Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1998
Initial Costs, Land		$ 1,865
Initial Costs, Building and Improvements		35,456
Costs Capitalized Subsequent to Acquisition	[1]	11,139
Gross Amount at Which Carried at Close of Period, Land	[2]	1,865
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	46,595
Total	[3]	48,460
Accumulated Depreciation	[4]	$ 20,169
Office [Member] | 9 Campus Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		2001
Initial Costs, Land		$ 3,277
Initial Costs, Building and Improvements		11,796
Costs Capitalized Subsequent to Acquisition	[1]	22,609
Gross Amount at Which Carried at Close of Period, Land	[2]	5,842
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	31,840
Total	[3]	37,682
Accumulated Depreciation	[4]	$ 12,352
Office [Member] | 2 Dryden Way [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		1998
Initial Costs, Land		$ 778
Initial Costs, Building and Improvements		420
Costs Capitalized Subsequent to Acquisition	[1]	110
Gross Amount at Which Carried at Close of Period, Land	[2]	778
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	530
Total	[3]	1,308
Accumulated Depreciation	[4]	$ 302
Office [Member] | 4 Gatehall Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1988
Acquired		2000
Initial Costs, Land		$ 8,452
Initial Costs, Building and Improvements		33,929
Costs Capitalized Subsequent to Acquisition	[1]	5,302
Gross Amount at Which Carried at Close of Period, Land	[2]	8,452
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	39,231
Total	[3]	47,683
Accumulated Depreciation	[4]	$ 17,628
Office [Member] | 2 Hilton Court [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1991
Acquired		1998
Initial Costs, Land		$ 1,971
Initial Costs, Building and Improvements		32,007
Costs Capitalized Subsequent to Acquisition	[1]	4,474
Gross Amount at Which Carried at Close of Period, Land	[2]	1,971
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	36,481
Total	[3]	38,452
Accumulated Depreciation	[4]	$ 18,874
Office [Member] | 1 Sylvan Way [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1989
Acquired		1998
Initial Costs, Land		$ 1,689
Initial Costs, Building and Improvements		24,699
Costs Capitalized Subsequent to Acquisition	[1]	2,253
Gross Amount at Which Carried at Close of Period, Land	[2]	1,021
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	27,620
Total	[3]	28,641
Accumulated Depreciation	[4]	$ 13,301
Office [Member] | 3 Sylvan Way [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1988
Acquired		2015
Initial Costs, Land		$ 5,590
Initial Costs, Building and Improvements		4,710
Costs Capitalized Subsequent to Acquisition	[1]	4,033
Gross Amount at Which Carried at Close of Period, Land	[2]	5,590
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	8,743
Total	[3]	14,333
Accumulated Depreciation	[4]	$ 280
Office [Member] | 5 Sylvan Way [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1989
Acquired		1998
Initial Costs, Land		$ 1,160
Initial Costs, Building and Improvements		25,214
Costs Capitalized Subsequent to Acquisition	[1]	4,769
Gross Amount at Which Carried at Close of Period, Land	[2]	1,161
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	29,982
Total	[3]	31,143
Accumulated Depreciation	[4]	$ 13,950
Office [Member] | 7 Sylvan Way [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1998
Initial Costs, Land		$ 2,084
Initial Costs, Building and Improvements		26,083
Costs Capitalized Subsequent to Acquisition	[1]	14,805
Gross Amount at Which Carried at Close of Period, Land	[2]	2,084
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	40,888
Total	[3]	42,972
Accumulated Depreciation	[4]	$ 14,057
Office [Member] | 5 Wood Hollow Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1979
Acquired		2004
Initial Costs, Land		$ 5,302
Initial Costs, Building and Improvements		26,488
Costs Capitalized Subsequent to Acquisition	[1]	20,963
Gross Amount at Which Carried at Close of Period, Land	[2]	5,302
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	47,451
Total	[3]	52,753
Accumulated Depreciation	[4]	$ 19,473
Office [Member] | 721 Route 202/206 [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1989
Acquired		1997
Initial Costs, Land		$ 6,730
Initial Costs, Building and Improvements		26,919
Costs Capitalized Subsequent to Acquisition	[1]	(5,309)
Gross Amount at Which Carried at Close of Period, Land	[2]	5,067
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	23,273
Total	[3]	28,340
Accumulated Depreciation	[4]	$ 12,109
Office [Member] | 100 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1975
Acquired		1997
Initial Costs, Land		$ 220
Initial Costs, Building and Improvements		5,366
Costs Capitalized Subsequent to Acquisition	[1]	1,674
Gross Amount at Which Carried at Close of Period, Land	[2]	220
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	7,040
Total	[3]	7,260
Accumulated Depreciation	[4]	$ 3,422
Office [Member] | 101 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1971
Acquired		1997
Initial Costs, Land		$ 267
Initial Costs, Building and Improvements		5,838
Costs Capitalized Subsequent to Acquisition	[1]	(6,004)
Gross Amount at Which Carried at Close of Period, Land	[2]	101
Total	[3]	$ 101
Office [Member] | 1 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1980
Acquired		1997
Initial Costs, Land		$ 66
Initial Costs, Building and Improvements		1,711
Costs Capitalized Subsequent to Acquisition	[1]	210
Gross Amount at Which Carried at Close of Period, Land	[2]	66
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	1,921
Total	[3]	1,987
Accumulated Depreciation	[4]	$ 1,049
Office [Member] | 2 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1997
Initial Costs, Land		$ 109
Initial Costs, Building and Improvements		3,128
Costs Capitalized Subsequent to Acquisition	[1]	1,474
Gross Amount at Which Carried at Close of Period, Land	[2]	109
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,602
Total	[3]	4,711
Accumulated Depreciation	[4]	$ 2,696
Office [Member] | 7 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1998
Initial Costs, Land		$ 330
Initial Costs, Building and Improvements		13,013
Costs Capitalized Subsequent to Acquisition	[1]	2,929
Gross Amount at Which Carried at Close of Period, Land	[2]	330
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	15,942
Total	[3]	16,272
Accumulated Depreciation	[4]	$ 7,758
Office [Member] | 17 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1989
Acquired	[5]	1997
Initial Costs, Building and Improvements	[5]	$ 7,269
Costs Capitalized Subsequent to Acquisition	[1],[5]	1,484
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	8,753
Total	[3],[5]	8,753
Accumulated Depreciation	[4],[5]	$ 4,540
Office [Member] | 1 Barker Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1975
Acquired		1997
Initial Costs, Land		$ 208
Initial Costs, Building and Improvements		9,629
Costs Capitalized Subsequent to Acquisition	[1]	3,248
Gross Amount at Which Carried at Close of Period, Land	[2]	207
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	12,878
Total	[3]	13,085
Accumulated Depreciation	[4]	$ 6,406
Office [Member] | 3 Barker Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		1997
Initial Costs, Land		$ 122
Initial Costs, Building and Improvements		7,864
Costs Capitalized Subsequent to Acquisition	[1]	2,117
Gross Amount at Which Carried at Close of Period, Land	[2]	122
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	9,981
Total	[3]	10,103
Accumulated Depreciation	[4]	$ 5,076
Office [Member] | 1 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1982
Acquired		1997
Initial Costs, Land		$ 1,104
Initial Costs, Building and Improvements		11,904
Costs Capitalized Subsequent to Acquisition	[1]	3,815
Gross Amount at Which Carried at Close of Period, Land	[2]	1,105
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	15,718
Total	[3]	16,823
Accumulated Depreciation	[4]	$ 7,750
Office [Member] | 3 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1997
Initial Costs, Land		$ 385
Initial Costs, Building and Improvements		6,256
Costs Capitalized Subsequent to Acquisition	[1]	1,817
Gross Amount at Which Carried at Close of Period, Land	[2]	385
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	8,073
Total	[3]	8,458
Accumulated Depreciation	[4]	$ 4,219
Office [Member] | 3 Odell Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1984
Acquired		2003
Initial Costs, Land		$ 1,322
Initial Costs, Building and Improvements		4,777
Costs Capitalized Subsequent to Acquisition	[1]	2,332
Gross Amount at Which Carried at Close of Period, Land	[2]	1,322
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	7,109
Total	[3]	8,431
Accumulated Depreciation	[4]	$ 3,736
Office And Office/Flex Buildings [Member] | 600 Horizon Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2002
Acquired		2002
Initial Costs, Building and Improvements		$ 7,549
Costs Capitalized Subsequent to Acquisition	[1]	1,189
Gross Amount at Which Carried at Close of Period, Land	[2]	685
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	8,053
Total	[3]	8,738
Accumulated Depreciation	[4]	$ 3,218
Office And Office/Flex Buildings [Member] | 11 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1974
Acquired		1997
Initial Costs, Land		$ 149
Initial Costs, Building and Improvements		2,159
Costs Capitalized Subsequent to Acquisition	[1]	578
Gross Amount at Which Carried at Close of Period, Land	[2]	149
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,737
Total	[3]	2,886
Accumulated Depreciation	[4]	$ 1,452
Office And Office/Flex Buildings [Member] | 75 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		1997
Initial Costs, Land		$ 2,314
Initial Costs, Building and Improvements		4,716
Costs Capitalized Subsequent to Acquisition	[1]	57
Gross Amount at Which Carried at Close of Period, Land	[2]	2,314
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,773
Total	[3]	7,087
Accumulated Depreciation	[4]	$ 2,500
Office And Office/Flex Buildings [Member] | 125 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2002
Acquired		2002
Initial Costs, Land		$ 1,055
Initial Costs, Building and Improvements		3,676
Costs Capitalized Subsequent to Acquisition	[1]	(252)
Gross Amount at Which Carried at Close of Period, Land	[2]	1,055
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,424
Total	[3]	4,479
Accumulated Depreciation	[4]	$ 1,500
Office And Office/Flex Buildings [Member] | 150 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1975
Acquired		1997
Initial Costs, Land		$ 497
Initial Costs, Building and Improvements		7,030
Costs Capitalized Subsequent to Acquisition	[1]	2,156
Gross Amount at Which Carried at Close of Period, Land	[2]	497
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	9,186
Total	[3]	9,683
Accumulated Depreciation	[4]	$ 4,616
Office And Office/Flex Buildings [Member] | 175 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1973
Acquired		1997
Initial Costs, Land		$ 655
Initial Costs, Building and Improvements		7,473
Costs Capitalized Subsequent to Acquisition	[1]	953
Gross Amount at Which Carried at Close of Period, Land	[2]	655
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	8,426
Total	[3]	9,081
Accumulated Depreciation	[4]	$ 4,444
Office And Office/Flex Buildings [Member] | 200 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1974
Acquired		1997
Initial Costs, Land		$ 579
Initial Costs, Building and Improvements		6,620
Costs Capitalized Subsequent to Acquisition	[1]	1,667
Gross Amount at Which Carried at Close of Period, Land	[2]	579
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	8,287
Total	[3]	8,866
Accumulated Depreciation	[4]	$ 4,066
Office And Office/Flex Buildings [Member] | 250 Clearbrook Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1973
Acquired		1997
Initial Costs, Land		$ 867
Initial Costs, Building and Improvements		8,647
Costs Capitalized Subsequent to Acquisition	[1]	2,434
Gross Amount at Which Carried at Close of Period, Land	[2]	867
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	11,081
Total	[3]	11,948
Accumulated Depreciation	[4]	$ 5,458
Office And Office/Flex Buildings [Member] | 50 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1969
Acquired		1997
Initial Costs, Land		$ 237
Initial Costs, Building and Improvements		2,617
Costs Capitalized Subsequent to Acquisition	[1]	540
Gross Amount at Which Carried at Close of Period, Land	[2]	237
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,157
Total	[3]	3,394
Accumulated Depreciation	[4]	$ 1,620
Office And Office/Flex Buildings [Member] | 77 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1977
Acquired		1997
Initial Costs, Land		$ 34
Initial Costs, Building and Improvements		1,104
Costs Capitalized Subsequent to Acquisition	[1]	177
Gross Amount at Which Carried at Close of Period, Land	[2]	34
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	1,281
Total	[3]	1,315
Accumulated Depreciation	[4]	$ 695
Office And Office/Flex Buildings [Member] | 85 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1968
Acquired		1997
Initial Costs, Land		$ 155
Initial Costs, Building and Improvements		2,507
Costs Capitalized Subsequent to Acquisition	[1]	538
Gross Amount at Which Carried at Close of Period, Land	[2]	155
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,045
Total	[3]	3,200
Accumulated Depreciation	[4]	$ 1,560
Office And Office/Flex Buildings [Member] | 300 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1970
Acquired		1997
Initial Costs, Land		$ 460
Initial Costs, Building and Improvements		3,609
Costs Capitalized Subsequent to Acquisition	[1]	302
Gross Amount at Which Carried at Close of Period, Land	[2]	460
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,911
Total	[3]	4,371
Accumulated Depreciation	[4]	$ 2,015
Office And Office/Flex Buildings [Member] | 350 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1970
Acquired		1997
Initial Costs, Land		$ 100
Initial Costs, Building and Improvements		1,793
Costs Capitalized Subsequent to Acquisition	[1]	175
Gross Amount at Which Carried at Close of Period, Land	[2]	100
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	1,968
Total	[3]	2,068
Accumulated Depreciation	[4]	$ 1,085
Office And Office/Flex Buildings [Member] | 399 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1962
Acquired		1997
Initial Costs, Land		$ 531
Initial Costs, Building and Improvements		7,191
Costs Capitalized Subsequent to Acquisition	[1]	163
Gross Amount at Which Carried at Close of Period, Land	[2]	531
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	7,354
Total	[3]	7,885
Accumulated Depreciation	[4]	$ 3,885
Office And Office/Flex Buildings [Member] | 400 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1970
Acquired		1997
Initial Costs, Land		$ 2,202
Initial Costs, Building and Improvements		1,846
Costs Capitalized Subsequent to Acquisition	[1]	1,140
Gross Amount at Which Carried at Close of Period, Land	[2]	2,202
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,986
Total	[3]	5,188
Accumulated Depreciation	[4]	$ 1,662
Office And Office/Flex Buildings [Member] | 500 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1970
Acquired		1997
Initial Costs, Land		$ 258
Initial Costs, Building and Improvements		4,183
Costs Capitalized Subsequent to Acquisition	[1]	384
Gross Amount at Which Carried at Close of Period, Land	[2]	258
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,567
Total	[3]	4,825
Accumulated Depreciation	[4]	$ 2,514
Office And Office/Flex Buildings [Member] | 525 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1972
Acquired		1997
Initial Costs, Land		$ 345
Initial Costs, Building and Improvements		5,499
Costs Capitalized Subsequent to Acquisition	[1]	900
Gross Amount at Which Carried at Close of Period, Land	[2]	345
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	6,399
Total	[3]	6,744
Accumulated Depreciation	[4]	$ 3,520
Office And Office/Flex Buildings [Member] | 1 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1967
Acquired		1997
Initial Costs, Land		$ 199
Initial Costs, Building and Improvements		2,023
Costs Capitalized Subsequent to Acquisition	[1]	152
Gross Amount at Which Carried at Close of Period, Land	[2]	199
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,175
Total	[3]	2,374
Accumulated Depreciation	[4]	$ 1,156
Office And Office/Flex Buildings [Member] | 2 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1968
Acquired		1997
Initial Costs, Land		$ 234
Initial Costs, Building and Improvements		2,726
Costs Capitalized Subsequent to Acquisition	[1]	914
Gross Amount at Which Carried at Close of Period, Land	[2]	234
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,640
Total	[3]	3,874
Accumulated Depreciation	[4]	$ 1,806
Office And Office/Flex Buildings [Member] | 3 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1969
Acquired		1997
Initial Costs, Land		$ 655
Initial Costs, Building and Improvements		7,936
Costs Capitalized Subsequent to Acquisition	[1]	1,407
Gross Amount at Which Carried at Close of Period, Land	[2]	655
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	9,343
Total	[3]	9,998
Accumulated Depreciation	[4]	$ 4,541
Office And Office/Flex Buildings [Member] | 4 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1969
Acquired		1997
Initial Costs, Land		$ 320
Initial Costs, Building and Improvements		3,729
Costs Capitalized Subsequent to Acquisition	[1]	1,979
Gross Amount at Which Carried at Close of Period, Land	[2]	320
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	5,708
Total	[3]	6,028
Accumulated Depreciation	[4]	$ 2,825
Office And Office/Flex Buildings [Member] | 5 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1969
Acquired		1997
Initial Costs, Land		$ 118
Initial Costs, Building and Improvements		1,949
Costs Capitalized Subsequent to Acquisition	[1]	374
Gross Amount at Which Carried at Close of Period, Land	[2]	118
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,323
Total	[3]	2,441
Accumulated Depreciation	[4]	$ 1,247
Office And Office/Flex Buildings [Member] | 6 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1968
Acquired		1997
Initial Costs, Land		$ 164
Initial Costs, Building and Improvements		1,998
Costs Capitalized Subsequent to Acquisition	[1]	160
Gross Amount at Which Carried at Close of Period, Land	[2]	164
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,158
Total	[3]	2,322
Accumulated Depreciation	[4]	$ 1,124
Office And Office/Flex Buildings [Member] | 7 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1972
Acquired		1997
Initial Costs, Land		$ 286
Initial Costs, Building and Improvements		4,321
Costs Capitalized Subsequent to Acquisition	[1]	1,166
Gross Amount at Which Carried at Close of Period, Land	[2]	286
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	5,487
Total	[3]	5,773
Accumulated Depreciation	[4]	$ 2,575
Office And Office/Flex Buildings [Member] | 8 Westchester Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1971
Acquired		1997
Initial Costs, Land		$ 447
Initial Costs, Building and Improvements		5,262
Costs Capitalized Subsequent to Acquisition	[1]	2,127
Gross Amount at Which Carried at Close of Period, Land	[2]	447
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	7,389
Total	[3]	7,836
Accumulated Depreciation	[4]	$ 3,709
Office And Office/Flex Buildings [Member] | 200 Saw Mill River Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1965
Acquired		1997
Initial Costs, Land		$ 353
Initial Costs, Building and Improvements		3,353
Costs Capitalized Subsequent to Acquisition	[1]	745
Gross Amount at Which Carried at Close of Period, Land	[2]	353
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,098
Total	[3]	4,451
Accumulated Depreciation	[4]	$ 2,037
Office And Office/Flex Buildings [Member] | 4 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1997
Initial Costs, Land		$ 363
Initial Costs, Building and Improvements		7,513
Costs Capitalized Subsequent to Acquisition	[1]	3,071
Gross Amount at Which Carried at Close of Period, Land	[2]	363
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	10,584
Total	[3]	10,947
Accumulated Depreciation	[4]	$ 6,190
Office And Office/Flex Buildings [Member] | 5 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1980
Acquired		2001
Initial Costs, Land		$ 2,219
Initial Costs, Building and Improvements		8,916
Costs Capitalized Subsequent to Acquisition	[1]	1,841
Gross Amount at Which Carried at Close of Period, Land	[2]	2,219
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	10,757
Total	[3]	12,976
Accumulated Depreciation	[4]	$ 5,495
Office And Office/Flex Buildings [Member] | 6 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1980
Acquired		2001
Initial Costs, Land		$ 740
Initial Costs, Building and Improvements		2,971
Costs Capitalized Subsequent to Acquisition	[1]	1,295
Gross Amount at Which Carried at Close of Period, Land	[2]	740
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	4,266
Total	[3]	5,006
Accumulated Depreciation	[4]	$ 2,582
Office And Office/Flex Buildings [Member] | 8 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1985
Acquired		1997
Initial Costs, Land		$ 212
Initial Costs, Building and Improvements		4,410
Costs Capitalized Subsequent to Acquisition	[1]	777
Gross Amount at Which Carried at Close of Period, Land	[2]	212
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	5,187
Total	[3]	5,399
Accumulated Depreciation	[4]	$ 2,893
Office And Office/Flex Buildings [Member] | 10 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1985
Acquired		1997
Initial Costs, Land		$ 134
Initial Costs, Building and Improvements		2,799
Costs Capitalized Subsequent to Acquisition	[1]	812
Gross Amount at Which Carried at Close of Period, Land	[2]	134
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,611
Total	[3]	3,745
Accumulated Depreciation	[4]	$ 2,121
Office And Office/Flex Buildings [Member] | 11 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1989
Acquired	[5]	1997
Initial Costs, Building and Improvements	[5]	$ 4,788
Costs Capitalized Subsequent to Acquisition	[1],[5]	763
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	5,551
Total	[3],[5]	5,551
Accumulated Depreciation	[4],[5]	$ 2,741
Office And Office/Flex Buildings [Member] | 12 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1999
Acquired	[5]	1999
Initial Costs, Land	[5]	$ 1,562
Initial Costs, Building and Improvements	[5]	3,254
Costs Capitalized Subsequent to Acquisition	[1],[5]	218
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	1,320
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	3,714
Total	[3],[5]	5,034
Accumulated Depreciation	[4],[5]	$ 1,790
Office And Office/Flex Buildings [Member] | 15 Skyline Drive [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1989
Acquired	[5]	1997
Initial Costs, Building and Improvements	[5]	$ 7,449
Costs Capitalized Subsequent to Acquisition	[1],[5]	1,749
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	9,198
Total	[3],[5]	9,198
Accumulated Depreciation	[4],[5]	$ 4,220
Office And Office/Flex Buildings [Member] | 100 Corporate Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1997
Initial Costs, Land		$ 602
Initial Costs, Building and Improvements		9,910
Costs Capitalized Subsequent to Acquisition	[1]	1,334
Gross Amount at Which Carried at Close of Period, Land	[2]	602
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	11,244
Total	[3]	11,846
Accumulated Depreciation	[4]	$ 5,973
Office And Office/Flex Buildings [Member] | 200 Corporate Boulevard South [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		1997
Initial Costs, Land		$ 502
Initial Costs, Building and Improvements		7,575
Costs Capitalized Subsequent to Acquisition	[1]	3,116
Gross Amount at Which Carried at Close of Period, Land	[2]	502
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	10,691
Total	[3]	11,193
Accumulated Depreciation	[4]	$ 5,159
Office And Office/Flex Buildings [Member] | 4 Executive Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1986
Acquired		1997
Initial Costs, Land		$ 584
Initial Costs, Building and Improvements		6,134
Costs Capitalized Subsequent to Acquisition	[1]	995
Gross Amount at Which Carried at Close of Period, Land	[2]	584
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	7,129
Total	[3]	7,713
Accumulated Depreciation	[4]	$ 3,664
Office And Office/Flex Buildings [Member] | 6 Executive Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1987
Acquired		1997
Initial Costs, Land		$ 546
Initial Costs, Building and Improvements		7,246
Costs Capitalized Subsequent to Acquisition	[1]	2,360
Gross Amount at Which Carried at Close of Period, Land	[2]	546
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	9,606
Total	[3]	10,152
Accumulated Depreciation	[4]	$ 4,942
Office And Office/Flex Buildings [Member] | 1 Odell Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1980
Acquired		1997
Initial Costs, Land		$ 1,206
Initial Costs, Building and Improvements		6,815
Costs Capitalized Subsequent to Acquisition	[1]	2,367
Gross Amount at Which Carried at Close of Period, Land	[2]	1,206
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	9,182
Total	[3]	10,388
Accumulated Depreciation	[4]	$ 4,775
Office And Office/Flex Buildings [Member] | 5 Odell Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1983
Acquired		1997
Initial Costs, Land		$ 331
Initial Costs, Building and Improvements		2,988
Costs Capitalized Subsequent to Acquisition	[1]	535
Gross Amount at Which Carried at Close of Period, Land	[2]	331
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,523
Total	[3]	3,854
Accumulated Depreciation	[4]	$ 1,990
Office And Office/Flex Buildings [Member] | 7 Odell Plaza [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1984
Acquired		1997
Initial Costs, Land		$ 419
Initial Costs, Building and Improvements		4,418
Costs Capitalized Subsequent to Acquisition	[1]	1,366
Gross Amount at Which Carried at Close of Period, Land	[2]	419
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	5,784
Total	[3]	6,203
Accumulated Depreciation	[4]	$ 2,886
Office And Office/Flex Buildings [Member] | 419 West Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1986
Acquired		1997
Initial Costs, Land		$ 4,538
Initial Costs, Building and Improvements		9,246
Costs Capitalized Subsequent to Acquisition	[1]	482
Gross Amount at Which Carried at Close of Period, Land	[2]	4,538
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	9,728
Total	[3]	14,266
Accumulated Depreciation	[4]	$ 5,060
Office And Office/Flex Buildings [Member] | 500 West Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1988
Acquired		1997
Initial Costs, Land		$ 415
Initial Costs, Building and Improvements		1,679
Costs Capitalized Subsequent to Acquisition	[1]	646
Gross Amount at Which Carried at Close of Period, Land	[2]	415
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,325
Total	[3]	2,740
Accumulated Depreciation	[4]	$ 1,098
Office And Office/Flex Buildings [Member] | 550 West Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1990
Acquired		1997
Initial Costs, Land		$ 1,975
Initial Costs, Building and Improvements		3,856
Costs Capitalized Subsequent to Acquisition	[1]	133
Gross Amount at Which Carried at Close of Period, Land	[2]	1,975
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,989
Total	[3]	5,964
Accumulated Depreciation	[4]	$ 2,065
Office And Office/Flex Buildings [Member] | 600 West Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1999
Acquired		1999
Initial Costs, Land		$ 2,305
Initial Costs, Building and Improvements		2,863
Costs Capitalized Subsequent to Acquisition	[1]	1,005
Gross Amount at Which Carried at Close of Period, Land	[2]	2,305
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,868
Total	[3]	6,173
Accumulated Depreciation	[4]	$ 1,611
Office And Office/Flex Buildings [Member] | 650 West Avenue [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1998
Acquired		1998
Initial Costs, Land		$ 1,328
Costs Capitalized Subsequent to Acquisition	[1]	3,268
Gross Amount at Which Carried at Close of Period, Land	[2]	1,328
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	3,268
Total	[3]	4,596
Accumulated Depreciation	[4]	$ 1,613
Industrial/Warehouse Facilities [Member] | 1 Warehouse Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1957
Acquired	[5]	1997
Initial Costs, Land	[5]	$ 3
Initial Costs, Building and Improvements	[5]	268
Costs Capitalized Subsequent to Acquisition	[1],[5]	208
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	3
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	476
Total	[3],[5]	479
Accumulated Depreciation	[4],[5]	$ 240
Industrial/Warehouse Facilities [Member] | 2 Warehouse Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1957
Acquired	[5]	1997
Initial Costs, Land	[5]	$ 4
Initial Costs, Building and Improvements	[5]	672
Costs Capitalized Subsequent to Acquisition	[1],[5]	341
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	4
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	1,013
Total	[3],[5]	1,017
Accumulated Depreciation	[4],[5]	$ 444
Industrial/Warehouse Facilities [Member] | 3 Warehouse Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1957
Acquired	[5]	1997
Initial Costs, Land	[5]	$ 21
Initial Costs, Building and Improvements	[5]	1,948
Costs Capitalized Subsequent to Acquisition	[1],[5]	363
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	21
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	2,311
Total	[3],[5]	2,332
Accumulated Depreciation	[4],[5]	$ 1,314
Industrial/Warehouse Facilities [Member] | 4 Warehouse Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1957
Acquired	[5]	1997
Initial Costs, Land	[5]	$ 84
Initial Costs, Building and Improvements	[5]	13,393
Costs Capitalized Subsequent to Acquisition	[1],[5]	3,665
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	85
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	17,057
Total	[3],[5]	17,142
Accumulated Depreciation	[4],[5]	$ 8,441
Industrial/Warehouse Facilities [Member] | 5 Warehouse Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1957
Acquired	[5]	1997
Initial Costs, Land	[5]	$ 19
Initial Costs, Building and Improvements	[5]	4,804
Costs Capitalized Subsequent to Acquisition	[1],[5]	884
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	19
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	5,688
Total	[3],[5]	5,707
Accumulated Depreciation	[4],[5]	$ 3,053
Industrial/Warehouse Facilities [Member] | 6 Warehouse Lane [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built	[5]	1982
Acquired	[5]	1997
Initial Costs, Land	[5]	$ 10
Initial Costs, Building and Improvements	[5]	4,419
Costs Capitalized Subsequent to Acquisition	[1],[5]	2,381
Gross Amount at Which Carried at Close of Period, Land	[2],[5]	10
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2],[5]	6,800
Total	[3],[5]	6,810
Accumulated Depreciation	[4],[5]	$ 3,246
Retail [Member] | 230 White Plains Road [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1984
Acquired		1997
Initial Costs, Land		$ 124
Initial Costs, Building and Improvements		1,845
Costs Capitalized Subsequent to Acquisition	[1]	288
Gross Amount at Which Carried at Close of Period, Land	[2]	124
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,133
Total	[3]	2,257
Accumulated Depreciation	[4]	$ 1,045
Retail [Member] | 2 Executive Boulevard [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1986
Acquired		1997
Initial Costs, Land		$ 89
Initial Costs, Building and Improvements		2,439
Costs Capitalized Subsequent to Acquisition	[1]	107
Gross Amount at Which Carried at Close of Period, Land	[2]	89
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	2,546
Total	[3]	2,635
Accumulated Depreciation	[4]	$ 1,324
Multi-Family Properties [Member] | RoseGarden Monaco, L.L.C. [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2011
Acquired		2017
Related Encumbrances		$ 169,988
Initial Costs, Land		58,761
Initial Costs, Building and Improvements		240,870
Costs Capitalized Subsequent to Acquisition	[1]	11
Gross Amount at Which Carried at Close of Period, Land	[2]	58,761
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	240,881
Total	[3]	299,642
Accumulated Depreciation	[4]	$ 4,590
Multi-Family Properties [Member] | Richmond Court [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1997
Acquired		2013
Initial Costs, Land		$ 2,992
Initial Costs, Building and Improvements		13,534
Costs Capitalized Subsequent to Acquisition	[1]	1,908
Gross Amount at Which Carried at Close of Period, Land	[2]	2,992
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	15,442
Total	[3]	18,434
Accumulated Depreciation	[4]	$ 1,417
Multi-Family Properties [Member] | Riverwatch Commons [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		1995
Acquired		2013
Initial Costs, Land		$ 4,169
Initial Costs, Building and Improvements		18,974
Costs Capitalized Subsequent to Acquisition	[1]	2,177
Gross Amount at Which Carried at Close of Period, Land	[2]	4,169
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	21,151
Total	[3]	25,320
Accumulated Depreciation	[4]	$ 1,951
Multi-Family Properties [Member] | Park Square [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2011
Acquired		2013
Related Encumbrances		$ 26,526
Initial Costs, Land		4,000
Initial Costs, Building and Improvements		40,670
Costs Capitalized Subsequent to Acquisition	[1]	294
Gross Amount at Which Carried at Close of Period, Land	[2]	4,000
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	40,964
Total	[3]	44,964
Accumulated Depreciation	[4]	$ 4,192
Multi-Family Properties [Member] | Quarry Place At Tuckahoe [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2016
Acquired		2016
Related Encumbrances		$ 40,367
Initial Costs, Land		5,585
Initial Costs, Building and Improvements		3,400
Costs Capitalized Subsequent to Acquisition	[1]	48,632
Gross Amount at Which Carried at Close of Period, Land	[2]	5,585
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	52,032
Total	[3]	57,617
Accumulated Depreciation	[4]	$ 1,163
Multi-Family Properties [Member] | Chase At Overlook Ridge [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2016
Acquired		2016
Related Encumbrances		$ 74,988
Initial Costs, Land		11,072
Initial Costs, Building and Improvements		87,793
Costs Capitalized Subsequent to Acquisition	[1]	269
Gross Amount at Which Carried at Close of Period, Land	[2]	11,072
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	88,062
Total	[3]	99,134
Accumulated Depreciation	[4]	$ 4,577
Multi-Family Properties [Member] | The Chase II At Overlook Ridge [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2016
Acquired		2016
Related Encumbrances		$ 59,697
Initial Costs, Land		10,755
Initial Costs, Building and Improvements		10,846
Costs Capitalized Subsequent to Acquisition	[1]	52,598
Gross Amount at Which Carried at Close of Period, Land	[2]	10,755
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	63,444
Total	[3]	74,199
Accumulated Depreciation	[4]	$ 1,390
Multi-Family Properties [Member] | Portside At Pier One [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2016
Acquired		2016
Related Encumbrances		$ 58,566
Initial Costs, Building and Improvements		73,713
Costs Capitalized Subsequent to Acquisition	[1]	9
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	73,722
Total	[3]	73,722
Accumulated Depreciation	[4]	$ 3,908
Multi-Family Properties [Member] | Alterra At Overlook Ridge IA [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2004
Acquired		2013
Related Encumbrances		$ 40,061
Initial Costs, Land		9,042
Initial Costs, Building and Improvements		50,671
Costs Capitalized Subsequent to Acquisition	[1]	956
Gross Amount at Which Carried at Close of Period, Land	[2]	9,042
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	51,627
Total	[3]	60,669
Accumulated Depreciation	[4]	$ 6,559
Multi-Family Properties [Member] | Alterra at Overlook Ridge II [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Year Built		2008
Acquired		2013
Related Encumbrances		$ 59,309
Initial Costs, Land		12,055
Initial Costs, Building and Improvements		71,409
Costs Capitalized Subsequent to Acquisition	[1]	299
Gross Amount at Which Carried at Close of Period, Land	[2]	12,056
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	71,707
Total	[3]	83,763
Accumulated Depreciation	[4]	9,058
Projects Under Development And Developable Land [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Related Encumbrances		184,984
Initial Costs, Land		399,372
Initial Costs, Building and Improvements		677,593
Gross Amount at Which Carried at Close of Period, Land	[2]	399,372
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	677,593
Total	[3]	1,076,965
Accumulated Depreciation	[4]	33,278
Furniture, Fixtures And Equipment [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Costs Capitalized Subsequent to Acquisition	[1]	30,247
Gross Amount at Which Carried at Close of Period, Building and Improvements	[2]	30,247
Total	[3]	30,247
Accumulated Depreciation	[4]	$ 11,031
Buildings And Improvements [Member]
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Useful Live		40 years
[1] These costs are net of impairments recorded, if any. [2] The aggregate cost for federal income tax purposes at December 31, 2017 was approximately $3.9 billion. [3] Properties identified as held for sale at December 31, 2017 are excluded. [4] Depreciation of buildings and improvements are calculated over lives ranging from the life of the lease to 40 years. [5] This property is located on land leased by the Company.