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, 2013	$ 7,043,618	$ 1,530	$ 200,000	$ 5,662,453	$ (108,552)	$ (2,722)	$ (11,556)	$ 1,302,465
Equity, shares at Dec. 31, 2013		152,983,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		70,000
Conversion of operating partnership units to Common Stock, value	0	$ 1		2,367				(2,368)
Conversions of redeemable preferred units to common units	33,306							33,306
Allocated net income for the year	304,822				266,326			38,496
Dividends/distributions declared	(340,766)				(306,340)
Dividends/distributions declared								(34,426)
Shares issued pursuant to stock purchase plan, shares		7,000
Shares issued pursuant to stock purchase plan, value	761			761
Net activity from stock option and incentive plan, shares		40,000
Net activity from stock option and incentive plan, value	22,215	$ 0		5,177				17,038
Contributions from noncontrolling interests in property partnerships	2,980							2,980
Distributions to noncontrolling interests in property partnerships	(21,224)							(21,224)
Amortization of interest rate contracts	1,881						1,690	191
Reallocation of noncontrolling interest	0			13,891				(13,891)
Equity, value at Sep. 30, 2014	7,047,593	$ 1,531	200,000	5,684,649	(148,566)	(2,722)	(9,866)	1,322,567
Equity, shares at Sep. 30, 2014		153,100,000
Equity, value at Dec. 31, 2014	$ 7,902,936	$ 1,531	200,000	6,270,257	(762,464)	(2,722)	(9,304)	2,205,638
Equity, shares at Dec. 31, 2014	153,113,945	153,114,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		419,000
Conversion of operating partnership units to Common Stock, value		$ 5		14,152				(14,157)
Conversions of redeemable preferred units to common units	$ 0
Allocated net income for the year	628,053				442,556			185,497
Dividends/distributions declared	(342,453)				(307,146)
Dividends/distributions declared								(35,307)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	780			780
Net activity from stock option and incentive plan, shares		36,000
Net activity from stock option and incentive plan, value	33,907			4,600				29,307
Acquisition of redeemable noncontrolling interest in property partnership	(1,586)			(1,586)
Contributions from noncontrolling interests in property partnerships	1,758							1,758
Distributions to noncontrolling interests in property partnerships	(144,468)							(144,468)
Effective portion of interest rate contracts	(18,050)						(13,008)	(5,042)
Amortization of interest rate contracts	1,882						1,687	195
Reallocation of noncontrolling interest				12,577				(12,577)
Equity, value at Sep. 30, 2015	$ 8,062,759	$ 1,536	$ 200,000	$ 6,300,780	$ (627,054)	$ (2,722)	$ (20,625)	$ 2,210,844
Equity, shares at Sep. 30, 2015	153,574,600	153,575,000