Annual report pursuant to Section 13 and 15(d)

Condensed Quarterly Financial Information (Summary Of Condensed Quarterly Financial Information) (Details)

v3.8.0.1
Condensed Quarterly Financial Information (Summary Of Condensed Quarterly Financial Information) (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Condensed Quarterly Financial Information [Abstract]                      
Total revenues $ 143,529 $ 160,018 $ 162,766 $ 149,887 $ 153,731 $ 157,517 $ 149,227 $ 152,923 $ 616,200 $ 613,398 $ 594,883
Net income (loss) 5,411 44,703 (39,125) 22,729 16,764 (9,605) 54,366 68,769 33,718 130,294 (142,052)
Net income (loss) available to common shareholders $ 2,582 $ 38,054 $ (37,330) $ 19,879 $ 15,181 $ (8,541) $ 48,393 $ 62,191 $ 23,185 $ 117,224 $ (125,752)
Basic earnings per common share:                      
Net income (loss) available to common shareholders $ (0.01) $ 0.39 $ (0.44) $ 0.11 $ 0.17 $ (0.10) $ 0.54 $ 0.69 $ 0.06 $ 1.31 $ (1.41)
Diluted earnings per common share:                      
Net income (loss) available to common shareholders $ (0.01) $ 0.39 $ (0.44) $ 0.11 $ 0.17 $ (0.10) $ 0.54 $ 0.69 $ 0.06 $ 1.30 $ (1.41)