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	202,127					199,139	199,139	456	2,532	2,988
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(18,138)				(17,020)		(17,020)	(42)	(1,076)	(1,118)
Amounts reclassified from accumulated other comprehensive loss	2,085				2,143		2,143	6	(64)	(58)
Deferred compensation plan, net			(3,024)	3,024
Restricted stock issued, net of amortization	12,127	2		12,125			12,127
Common stock issued for stock based compensation, net	(5,857)			(5,857)			(5,857)
Common stock repurchased and retired	(32,777)	(5)		(32,772)			(32,777)
Common stock issued under dividend reinvestment plan	1,085			1,085			1,085
Contributions from partners	1,999								1,999	1,999
Issuance of exchangeable operating partnership units	25,869							25,869		25,869
Distributions to partners	(4,222)								(4,222)	(4,222)
Cash dividends declared - common stock/unit	(294,619)					(294,005)	(294,005)	(614)		(614)
Reallocation of limited partner's interest				(66)			(66)		66	66
Ending Balance at Sep. 30, 2019	6,339,847	1,676	(22,858)	7,650,056	(15,804)	(1,350,331)	6,262,739	36,341	40,767	77,108
Beginning 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	57,944					56,965	56,965	157	822	979
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(3,682)				(3,406)		(3,406)	(13)	(263)	(276)
Amounts reclassified from accumulated other comprehensive loss	1,677				1,688		1,688	5	(16)	(11)
Deferred compensation plan, net			(322)	322
Restricted stock issued, net of amortization	4,224			4,224			4,224
Common stock issued for stock based compensation, net	100			100			100
Common stock issued under dividend reinvestment plan	345			345			345
Contributions from partners	103								103	103
Issuance of exchangeable operating partnership units	25,869							25,869		25,869
Distributions to partners	(1,358)								(1,358)	(1,358)
Cash dividends declared - common stock/unit	(98,223)					(98,018)	(98,018)	(205)		(205)
Ending Balance at Sep. 30, 2019	6,339,847	1,676	(22,858)	7,650,056	(15,804)	(1,350,331)	6,262,739	36,341	40,767	77,108
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	8,101					6,402	6,402	29	1,670	1,699
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(18,808)				(17,505)		(17,505)	(79)	(1,224)	(1,303)
Amounts reclassified from accumulated other comprehensive loss	6,479				6,282		6,282	28	169	197
Deferred compensation plan, net	207		(1,488)	1,695			207
Restricted stock issued, net of amortization	10,964	2		10,962			10,964
Common stock issued for stock based compensation, net	(5,172)			(5,172)			(5,172)
Common stock issued under dividend reinvestment plan	1,138			1,138			1,138
Common stock issued, net of issuance costs	125,608	19		125,589			125,608
Contributions from partners	443								443	443
Issuance of exchangeable operating partnership units	1,275							1,275		1,275
Distributions to partners	(4,029)								(4,029)	(4,029)
Cash dividends declared - common stock/unit	(303,044)					(301,678)	(301,678)	(1,366)		(1,366)
Ending Balance at Sep. 30, 2020	6,113,123	1,697	(24,687)	7,789,142	(23,220)	(1,703,338)	6,039,594	35,987	37,542	73,529
Beginning 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,310					12,688	12,688	57	565	622
Other comprehensive income (loss):
Other comprehensive loss before reclassification	(613)				(551)		(551)	(2)	(60)	(62)
Amounts reclassified from accumulated other comprehensive loss	2,570				2,466		2,466	11	93	104
Deferred compensation plan, net	207		(90)	297			207
Restricted stock issued, net of amortization	3,372			3,372			3,372
Common stock issued for stock based compensation, net of common stock redeemed for taxes withheld	3			3			3
Common stock issued under dividend reinvestment plan	382			382			382
Common stock issued, net of issuance costs	(7)			(7)			(7)
Contributions from partners	312								312	312
Distributions to partners	(2,211)								(2,211)	(2,211)
Cash dividends declared - common stock/unit	(101,404)					(100,949)	(100,949)	(455)		(455)
Ending Balance at Sep. 30, 2020	$ 6,113,123	$ 1,697	$ (24,687)	$ 7,789,142	$ (23,220)	$ (1,703,338)	$ 6,039,594	$ 35,987	$ 37,542	$ 73,529