CONSOLIDATED STATEMENT OF EQUITY - USD ($) $ in Thousands	Total	Preferred Shares [Member]	Common Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Distributions in Excess of Net Income [Member]	Deferred Compensation Obligation [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock at Cost [Member]	Non-Controlling Interests [Member]
Balance at Dec. 31, 2017	$ 2,897,438	$ 525,000	$ 18,426	$ 5,531,249	$ (3,183,134)	$ 8,777	$ (1,106)	$ (8,280)	$ 6,506
Issuance of common shares related to stock plans	5,865	0	41	5,824	0	0	0	0	0
Stock-based compensation, net	2,785	0	0	3,015	0	(1,109)	0	879	0
Distributions to non-controlling interests	(193)	0	0	0	0	0	0	0	(193)
Redemption of OP Units	(709)	0	0	880	0	0	0	0	(1,589)
Dividends declared-common shares	(70,304)	0	0	0	(70,304)	0	0	0	0
Dividends declared-preferred shares	(8,383)	0	0	0	(8,383)	0	0	0	0
Comprehensive (loss) income	(54,176)	0	0	0	(54,153)	0	(205)	0	182
Balance at Mar. 31, 2018	2,772,323	525,000	18,467	5,540,968	(3,315,974)	7,668	(1,311)	(7,401)	4,906
Balance at Dec. 31, 2018	2,073,002	525,000	18,471	5,544,220	(3,980,151)	8,193	(1,381)	(44,278)	2,928
Issuance of common shares related to stock plans	32	0	1	31	0	0	0	0	0
Repurchase of common shares	(14,069)	0	0	0	0	0	0	(14,069)	0
Stock-based compensation, net	2,449	0	0	1,044	0	(239)	0	1,644	0
Distributions to non-controlling interests	(212)	0	0	0	0	0	0	0	(212)
Dividends declared-common shares	(36,252)	0	0	0	(36,252)	0	0	0	0
Dividends declared-preferred shares	(8,383)	0	0	0	(8,383)	0	0	0	0
Comprehensive (loss) income	36,399	0	0	0	35,790	0	304	0	305
Balance at Mar. 31, 2019	$ 2,052,966	$ 525,000	$ 18,472	$ 5,545,295	$ (3,988,996)	$ 7,954	$ (1,077)	$ (56,703)	$ 3,021