Consolidated Statement of Equity - USD ($)	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, 2017	$ 6,733,054,000	$ 1,714,000	$ (18,307,000)	$ 7,873,104,000	$ (6,289,000)	$ (1,158,170,000)	$ 6,692,052,000	$ 10,907,000	$ 30,095,000	$ 41,002,000
Adjustment due to change in accounting policy (note 1) at Dec. 31, 2017	30,903,000				12,000	30,889,000	30,901,000		2,000	2,000
Adjusted balance at Dec. 31, 2017	6,763,957,000	1,714,000	(18,307,000)	7,873,104,000	(6,277,000)	(1,127,281,000)	6,722,953,000	10,907,000	30,097,000	41,004,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	252,325,000					249,127,000	249,127,000	525,000	2,673,000	3,198,000
Other comprehensive (loss) income:
Other comprehensive Income (loss) before reclassifications	307,000				36,000		36,000		271,000	271,000
Amounts reclassified from accumulated other comprehensive income	5,342,000				5,314,000		5,314,000	11,000	17,000	28,000
Deferred compensation plan, net	(13,000)		(1,527,000)	1,514,000			(13,000)
Restricted stock issued, net of amortization	16,745,000	2,000		16,743,000			16,745,000
Common stock redeemed for taxes withheld for stock based compensation, net	(6,373,000)			(6,373,000)			(6,373,000)
Common stock issued under dividend reinvestment plan	1,333,000			1,333,000			1,333,000
Common stock issued, net of issuance costs	10,000			10,000			10,000
Common stock repurchased and retired	(213,851,000)	(37,000)		(213,814,000)			(213,851,000)
Contributions from partners	13,000,000								13,000,000	13,000,000
Distributions to partners	(4,526,000)								(4,526,000)	(4,526,000)
Cash dividends declared:
Common stock/unit	(378,088,000)					(377,311,000)	(377,311,000)	(777,000)		(777,000)
Ending Balance at Dec. 31, 2018	6,450,168,000	1,679,000	(19,834,000)	7,672,517,000	(927,000)	(1,255,465,000)	6,397,970,000	10,666,000	41,532,000	52,198,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	243,258,000					239,430,000	239,430,000	634,000	3,194,000	3,828,000
Other comprehensive (loss) income:
Other comprehensive Income (loss) before reclassifications	(15,270,000)				(14,388,000)		(14,388,000)	(31,000)	(851,000)	(882,000)
Amounts reclassified from accumulated other comprehensive income	3,269,000				3,318,000		3,318,000	12,000	(61,000)	(49,000)
Deferred compensation plan, net			(3,365,000)	3,365,000
Restricted stock issued, net of amortization	16,254,000	2,000		16,252,000			16,254,000
Common stock redeemed for taxes withheld for stock based compensation, net	(5,794,000)			(5,794,000)			(5,794,000)
Common stock issued under dividend reinvestment plan	1,429,000	1,000		1,428,000			1,429,000
Common stock repurchased and retired	(32,778,000)	(6,000)		(32,772,000)			(32,778,000)
Contributions from partners	2,151,000								2,151,000	2,151,000
Issuance of exchangeable operating partnership units	25,870,000							25,870,000		25,870,000
Distributions to partners	(5,518,000)								(5,518,000)	(5,518,000)
Cash dividends declared:
Common stock/unit	(393,078,000)					(392,027,000)	(392,027,000)	(1,051,000)		(1,051,000)
Ending Balance at Dec. 31, 2019	6,289,961,000	1,676,000	(23,199,000)	7,654,930,000	(11,997,000)	(1,408,062,000)	6,213,348,000	36,100,000	40,513,000	76,613,000
Cash dividends declared:
Reallocation of limited partners' interest				(66,000)			(66,000)		66,000	66,000
Net income	47,317,000					44,889,000	44,889,000	203,000	2,225,000	2,428,000
Other comprehensive Income (loss) before reclassifications	(18,867,000)				(17,589,000)		(17,589,000)	(79,000)	(1,199,000)	(1,278,000)
Amounts reclassified from accumulated other comprehensive income	11,262,000				10,961,000		10,961,000	50,000	251,000	301,000
Deferred compensation plan, net			(1,237,000)	1,237,000
Restricted stock issued, net of amortization	14,248,000	2,000		14,246,000			14,248,000
Common stock redeemed for taxes withheld for stock based compensation, net	(5,059,000)			(5,059,000)			(5,059,000)
Common stock issued under dividend reinvestment plan	1,139,000			1,139,000			1,139,000
Common stock issued, net of issuance costs	125,608,000	19,000		125,589,000			125,608,000
Common stock repurchased and retired	0
Contributions from partners	606,000								606,000	606,000
Issuance of exchangeable operating partnership units	1,275,000							1,275,000		1,275,000
Distributions to partners	(4,888,000)								(4,888,000)	(4,888,000)
Common stock/unit	(404,455,000)					(402,633,000)	(402,633,000)	(1,822,000)		(1,822,000)
Ending Balance at Dec. 31, 2020	$ 6,058,147,000	$ 1,697,000	$ (24,436,000)	$ 7,792,082,000	$ (18,625,000)	$ (1,765,806,000)	$ 5,984,912,000	$ 35,727,000	$ 37,508,000	$ 73,235,000