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) |