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]
Beginning 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 income	36,399	0	0	0	35,790	0	304	0	305
Ending 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
Beginning Balance at Dec. 31, 2019	1,981,478	325,000	19,382	5,700,400	(4,066,099)	7,929	(491)	(7,707)	3,064
Issuance of common shares related to stock plans	126	0	17	109	0	0	0	0	0
Repurchase of common shares	(7,500)	0	0	0	0	0	0	(7,500)	0
Stock-based compensation, net	2,684	0	0	3,012	0	(1,935)	0	1,607	0
Distributions to non-controlling interests	(278)	0	0	0	0	0	0	0	(278)
Dividends declared-common shares	(38,914)	0	0	0	(38,914)	0	0	0	0
Dividends declared-preferred shares	(5,133)	0	0	0	(5,133)	0	0	0	0
Comprehensive income	35,015	0	0	0	34,333	0	387	0	295
Ending Balance at Mar. 31, 2020	$ 1,967,478	$ 325,000	$ 19,399	$ 5,703,521	$ (4,075,813)	$ 5,994	$ (104)	$ (13,600)	$ 3,081