| Discontinued Operations (Narrative) (Details) (USD $) In Thousands, unless otherwise specified | 9 Months Ended | 12 Months Ended | 
|---|---|---|
| Sep. 30, 2014
 item
 sqft | Dec. 31, 2013
 item
 property
 sqft | |
| Discontinued Operations [Abstract] | ||
| Number of properties sold | 16 | 24 | 
| Area of property sold | 2,610,931 | 3,000,000 | 
| Number of land parcels sold | 3 | |
| Sales proceeds | $ 319,239 | $ 390,600 | 
| X | ||||||||||
| 
- Definition Area Of Real Estate Property Sold No definition available. 
 | 
| X | ||||||||||
| 
- Definition Number Of Buildings On Properties Sold No definition available. 
 | 
| X | ||||||||||
| 
- Definition Number Of Land Parcels Sold No definition available. 
 | 
| X | ||||||||||
| 
- Details 
 | 
| X | ||||||||||
| 
- Definition Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 |