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, 2017	$ 6,733,054	$ 1,714	$ (18,307)	$ 7,873,104	$ (6,289)	$ (1,158,170)	$ 6,692,052	$ 10,907	$ 30,095	$ 41,002
Adjustment due to change inaccounting policy (note 1) at Dec. 31, 2017	30,903				12	30,889	30,901		2	2
Adjusted balance at Dec. 31, 2017	6,763,957	1,714	(18,307)	7,873,104	(6,277)	(1,127,281)	6,722,953	10,907	30,097	41,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	102,054					100,500	100,500	212	1,342	1,554
Other comprehensive income	17,272				16,594		16,594	35	643	678
Deferred compensation plan, net	(4)		(961)	957			(4)
Restricted stock issued, net of amortization	8,135	1		8,134			8,135
Common stock redeemed for taxes withheld for stock based compensation, net	(6,540)			(6,540)			(6,540)
Common stock repurchased and retired	(124,989)	(21)		(124,968)			(124,989)
Common stock issued under dividend reinvestment plan	678			678			678
Common stock issued, net of issuance costs	10			10			10
Distributions to partners	(2,159)								(2,159)	(2,159)
Cash dividends declared - common stock/unit	(189,626)					(189,237)	(189,237)	(389)		(389)
Ending Balance at Jun. 30, 2018	6,568,788	1,694	(19,268)	7,751,375	10,317	(1,216,018)	6,528,100	10,765	29,923	40,688
Beginning balance at Mar. 31, 2018	6,605,381	1,694	(18,756)	7,746,427	4,764	(1,169,828)	6,564,301	10,847	30,233	41,080
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	48,589					47,841	47,841	100	648	748
Other comprehensive income	5,748				5,553		5,553	12	183	195
Deferred compensation plan, net	(1)		(512)	511			(1)
Restricted stock issued, net of amortization	4,014			4,014			4,014
Common stock redeemed for taxes withheld for stock based compensation, net	103			103			103
Common stock issued under dividend reinvestment plan	320			320			320
Distributions to partners	(1,141)								(1,141)	(1,141)
Cash dividends declared - common stock/unit	(94,225)					(94,031)	(94,031)	(194)		(194)
Ending Balance at Jun. 30, 2018	6,568,788	1,694	(19,268)	7,751,375	10,317	(1,216,018)	6,528,100	10,765	29,923	40,688
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	144,183					142,174	142,174	299	1,710	2,009
Other comprehensive income	(14,048)				(13,159)		(13,159)	(28)	(861)	(889)
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)
Reallocation of limited partner's interest	0			(66)			(66)		66	66
Cash dividends declared - common stock/unit	(196,396)					(195,987)	(195,987)	(409)		(409)
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	52,690					51,728	51,728	109	853	962
Other comprehensive income	(8,520)				(7,990)		(7,990)	(17)	(513)	(530)
Deferred compensation plan, net	0		(1,310)	1,310
Restricted stock issued, net of amortization	3,952	1		3,951			3,952
Common stock redeemed for taxes withheld for stock based compensation, net	94			94			94
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