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, 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
Beginning Balance at Dec. 31, 2020	1,944,823	325,000	19,400	5,705,164	(4,099,534)	5,479	(2,682)	(11,319)	3,315
Issuance of common shares related to stock plans	37	0	6	31	0	0	0	0	0
Issuance of common shares for cash offering	225,529	0	1,696	219,910	0	0	0	3,923	0
Stock-based compensation, net	10,621	0	0	8,580	0	(968)	0	3,009	0
Distributions to non-controlling interests	(16)	0	0	0	0	0	0	0	(16)
Dividends declared-common shares	(23,303)	0	0	0	(23,303)	0	0	0	0
Dividends declared-preferred shares	(4,950)	0	0	0	(4,950)	0	0	0	0
Comprehensive income	18,863	0	0	0	16,008	0	2,682	0	173
Ending Balance at Mar. 31, 2021	$ 2,171,604	$ 325,000	$ 21,102	$ 5,933,685	$ (4,111,779)	$ 4,511	$ 0	$ (4,387)	$ 3,472