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	0	0	1	(1)	0	0	0	0	0
Repurchase of common shares	(14,069)	0	0	0	0	0	0	(14,069)	0
Stock-based compensation, net	3,729	0	0	2,188	0	(147)	0	1,688	0
Distributions to non-controlling interests	(379)	0	0	0	0	0	0	0	(379)
Dividends declared-common shares	(72,510)	0	0	0	(72,510)	0	0	0	0
Dividends declared-preferred shares	(16,766)	0	0	0	(16,766)	0	0	0	0
Comprehensive income (loss)	54,244	0	0	0	53,067	0	612	0	565
Ending Balance at Jun. 30, 2019	2,027,251	525,000	18,472	5,546,407	(4,016,360)	8,046	(769)	(56,659)	3,114
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
Comprehensive income (loss)	78,157
Ending Balance at Sep. 30, 2019	2,007,505	525,000	18,472	5,547,534	(4,037,373)	8,070	(757)	(56,520)	3,079
Beginning Balance at Jun. 30, 2019	2,027,251	525,000	18,472	5,546,407	(4,016,360)	8,046	(769)	(56,659)	3,114
Issuance of common shares related to stock plans	21	0	0	21	0	0	0	0	0
Stock-based compensation, net	1,269	0	0	1,106	0	24	0	139	0
Distributions to non-controlling interests	(306)	0	0	0	0	0	0	0	(306)
Dividends declared-common shares	(36,261)	0	0	0	(36,261)	0	0	0	0
Dividends declared-preferred shares	(8,382)	0	0	0	(8,382)	0	0	0	0
Comprehensive income (loss)	23,913	0	0	0	23,630	0	12	0	271
Ending Balance at Sep. 30, 2019	2,007,505	525,000	18,472	5,547,534	(4,037,373)	8,070	(757)	(56,520)	3,079
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	(60)	0	18	(78)	0	0	0	0	0
Repurchase of common shares	(7,500)	0	0	0	0	0	0	(7,500)	0
Stock-based compensation, net	4,440	0	0	4,397	0	(2,495)	0	2,538	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	(10,266)	0	0	0	(10,266)	0	0	0	0
Comprehensive income (loss)	30,904	0	0	0	29,720	0	679	0	505
Ending Balance at Jun. 30, 2020	1,959,804	325,000	19,400	5,704,719	(4,085,559)	5,434	188	(12,669)	3,291
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
Repurchase of common shares	(7,500)
Comprehensive income (loss)	34,391
Ending Balance at Sep. 30, 2020	1,959,712	325,000	19,400	5,706,225	(4,083,405)	5,442	(3,728)	(12,463)	3,241
Beginning Balance at Jun. 30, 2020	1,959,804	325,000	19,400	5,704,719	(4,085,559)	5,434	188	(12,669)	3,291
Stock-based compensation, net	1,720	0	0	1,506	0	8	0	206	0
Distributions to non-controlling interests	(166)	0	0	0	0	0	0	0	(166)
Dividends declared-preferred shares	(5,133)	0	0	0	(5,133)	0	0	0	0
Comprehensive income (loss)	3,487	0	0	0	7,287	0	(3,916)	0	116
Ending Balance at Sep. 30, 2020	$ 1,959,712	$ 325,000	$ 19,400	$ 5,706,225	$ (4,083,405)	$ 5,442	$ (3,728)	$ (12,463)	$ 3,241