Consolidated Statement of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Distributions in Excess of Net Income [Member]	Total Stockholders' Equity [Member]	Noncontrolling Interest Exchangeable Operating Partnership Units [Member]	Noncontrolling Interests in Limited Partners' Interest in Consolidated Partnerships [Member]	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2018	$ 6,450,168	$ 1,679	$ (19,834)	$ 7,672,517	$ (927)	$ (1,255,465)	$ 6,397,970	$ 10,666	$ 41,532	$ 52,198
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	144,183					142,174	142,174	299	1,710	2,009
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(14,456)				(13,614)		(13,614)	(29)	(813)	(842)
Amounts reclassified from accumulated other comprehensive loss	408				455		455	1	(48)	(47)
Deferred compensation plan, net	0		(2,702)	2,702
Restricted stock issued, net of amortization	7,904	3		7,901			7,904
Common stock redeemed for taxes withheld for stock based compensation, net	(5,957)			(5,957)			(5,957)
Common stock repurchased and retired	(32,778)	(6)		(32,772)			(32,778)
Common stock issued under dividend reinvestment plan	740			740			740
Contributions from partners	1,896								1,896	1,896
Distributions to partners	(2,864)								(2,864)	(2,864)
Cash dividends declared - common stock/unit	(196,396)					(195,987)	(195,987)	(409)		(409)
Reallocation of limited partner's interest	0			(66)			(66)		66	66
Ending Balance at Jun. 30, 2019	6,352,848	1,676	(22,536)	7,645,065	(14,086)	(1,309,278)	6,300,841	10,528	41,479	52,007
Beginning balance at Mar. 31, 2019	6,402,773	1,675	(21,226)	7,639,353	(6,096)	(1,263,011)	6,350,695	10,641	41,437	52,078
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	52,690					51,728	51,728	109	853	962
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(9,104)				(8,597)		(8,597)	(19)	(488)	(507)
Amounts reclassified from accumulated other comprehensive loss	584				607		607	2	(25)	(23)
Deferred compensation plan, net	0		(1,310)	1,310
Restricted stock issued, net of amortization	3,952	1		3,951			3,952
Common stock issued for stock based compensation, net of common stock redeemed for taxes withheld	0
Common stock redeemed for taxes withheld for stock based compensation, net	94			94			94
Common stock repurchased and retired	0
Common stock issued under dividend reinvestment plan	357			357			357
Contributions from partners	1,001								1,001	1,001
Distributions to partners	(1,299)								(1,299)	(1,299)
Cash dividends declared - common stock/unit	(98,200)					(97,995)	(97,995)	(205)		(205)
Ending Balance at Jun. 30, 2019	6,352,848	1,676	(22,536)	7,645,065	(14,086)	(1,309,278)	6,300,841	10,528	41,479	52,007
Beginning balance at Dec. 31, 2019	6,289,961	1,676	(23,199)	7,654,930	(11,997)	(1,408,062)	6,213,348	36,100	40,513	76,613
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(5,209)					(6,286)	(6,286)	(28)	1,105	1,077
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(18,195)				(16,954)		(16,954)	(77)	(1,164)	(1,241)
Amounts reclassified from accumulated other comprehensive loss	3,909				3,816		3,816	17	76	93
Deferred compensation plan, net	0		(1,398)	1,398
Restricted stock issued, net of amortization	7,592	2		7,590			7,592
Common stock redeemed for taxes withheld for stock based compensation, net	(5,175)			(5,175)			(5,175)
Common stock issued under dividend reinvestment plan	756			756			756
Common stock issued, net of issuance costs	125,615	19		125,596			125,615
Contributions from partners	131								131	131
Issuance of exchangeable operating partnership units	1,275							1,275		1,275
Distributions to partners	(1,818)								(1,818)	(1,818)
Cash dividends declared - common stock/unit	(201,640)					(200,729)	(200,729)	(911)		(911)
Ending Balance at Jun. 30, 2020	6,197,202	1,697	(24,597)	7,785,095	(25,135)	(1,615,077)	6,121,983	36,376	38,843	75,219
Beginning balance at Mar. 31, 2020	6,275,235	1,696	(23,897)	7,780,336	(25,531)	(1,533,182)	6,199,422	36,744	39,069	75,813
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	19,574					19,046	19,046	87	441	528
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(2,131)				(2,016)		(2,016)	(10)	(105)	(115)
Amounts reclassified from accumulated other comprehensive loss	2,484				2,412		2,412	11	61	72
Deferred compensation plan, net	0		(700)	700
Restricted stock issued, net of amortization	3,828	1		3,827			3,828
Common stock issued for stock based compensation, net of common stock redeemed for taxes withheld	13			13			13
Common stock issued under dividend reinvestment plan	377			377			377
Common stock issued, net of issuance costs	(158)			(158)			(158)
Contributions from partners	31								31	31
Distributions to partners	(654)								(654)	(654)
Cash dividends declared - common stock/unit	(101,397)					(100,941)	(100,941)	(456)		(456)
Ending Balance at Jun. 30, 2020	$ 6,197,202	$ 1,697	$ (24,597)	$ 7,785,095	$ (25,135)	$ (1,615,077)	$ 6,121,983	$ 36,376	$ 38,843	$ 75,219