Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Dividends In Excess Of Earnings [Member]	Treasury Stock, At Cost [Member]	Accumulated Other Comprehensive (Income) Loss [Member]	Noncontrolling Interests [Member]
Equity, value at Dec. 31, 2015	$ 7,886,927	$ 1,536	$ 200,000	$ 6,305,687	$ (780,952)	$ (2,722)	$ (14,114)	$ 2,177,492
Equity, shares at Dec. 31, 2015		153,580,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		78,000
Conversion of operating partnership units to Common Stock, value	0	$ 1		2,663				(2,664)
Allocated net income for the year	333,579				283,530			50,049
Dividends/distributions declared	(228,652)				(204,939)			(23,713)
Shares issued pursuant to stock purchase plan, shares		3,000
Shares issued pursuant to stock purchase plan, value	332			332
Net activity from stock option and incentive plan, shares		14,000
Net activity from stock option and incentive plan, value	16,649	$ 0		1,772				14,877
Sale of interests in property partnerships	0			1,320				(1,320)
Contributions from noncontrolling interests in property partnerships	5,040							5,040
Distributions to noncontrolling interests in property partnerships	(25,914)							(25,914)
Effective portion of interest rate contracts	(90,997)						(66,759)	(24,238)
Amortization of interest rate contracts	1,255						1,125	130
Reallocation of noncontrolling interest	0			4,417				(4,417)
Equity, value at Jun. 30, 2016	7,898,219	$ 1,537	200,000	6,316,191	(702,361)	(2,722)	(79,748)	2,165,322
Equity, shares at Jun. 30, 2016		153,675,000
Equity, value at Dec. 31, 2016	$ 7,931,924	$ 1,538	200,000	6,333,424	(693,694)	(2,722)	(52,251)	2,145,629
Equity, shares at Dec. 31, 2016	153,790,175	153,790,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		481,000
Conversion of operating partnership units to Common Stock, value		$ 5		16,417				(16,422)
Allocated net income for the year	$ 282,574				236,014			46,560
Dividends/distributions declared	(263,345)				(236,368)			(26,977)
Shares issued pursuant to stock purchase plan, shares		3,000
Shares issued pursuant to stock purchase plan, value	373			373
Net activity from stock option and incentive plan, shares		34,000
Net activity from stock option and incentive plan, value	21,168			1,980				19,188
Cumulative effect of a change in accounting principle	(2,035)				(272)			(1,763)
Contributions from noncontrolling interests in property partnerships	133,072							133,072
Distributions to noncontrolling interests in property partnerships	(26,949)							(26,949)
Effective portion of interest rate contracts	(6,133)						(3,301)	(2,832)
Amortization of interest rate contracts	2,703						2,391	312
Reallocation of noncontrolling interest				10,840				(10,840)
Equity, value at Jun. 30, 2017	$ 8,073,352	$ 1,543	$ 200,000	$ 6,363,034	$ (694,320)	$ (2,722)	$ (53,161)	$ 2,258,978
Equity, shares at Jun. 30, 2017	154,307,529	154,308,000