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		173,000
Conversion of operating partnership units to Common Stock, value	0	$ 2		5,879				(5,881)
Allocated net income for the year	405,083				362,910			42,173
Dividends/distributions declared	(342,980)				(307,480)			(35,500)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	730			730
Net activity from stock option and incentive plan, shares		14,000
Net activity from stock option and incentive plan, value	24,290	$ 0		2,870				21,420
Sale of interests in property partnerships	0			1,320				(1,320)
Contributions from noncontrolling interests in property partnerships	6,737							6,737
Distributions to noncontrolling interests in property partnerships	(38,694)							(38,694)
Effective portion of interest rate contracts	(85,285)						(62,022)	(23,263)
Amortization of interest rate contracts	2,445						2,193	252
Reallocation of noncontrolling interest	0			10,094				(10,094)
Equity, value at Sep. 30, 2016	7,859,253	$ 1,538	200,000	6,326,580	(725,522)	(2,722)	(73,943)	2,133,322
Equity, shares at Sep. 30, 2016		153,773,000
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		492,000
Conversion of operating partnership units to Common Stock, value		$ 5		16,807				(16,812)
Allocated net income for the year	$ 430,278				355,961			74,317
Dividends/distributions declared	(395,026)				(354,734)			(40,292)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	795			795
Net activity from stock option and incentive plan, shares		34,000
Net activity from stock option and incentive plan, value	29,191			2,920				26,271
Cumulative effect of a change in accounting principle	(2,035)				(272)			(1,763)
Contributions from noncontrolling interests in property partnerships	147,772							147,772
Distributions to noncontrolling interests in property partnerships	(41,439)							(41,439)
Effective portion of interest rate contracts	(6,133)						(3,304)	(2,829)
Amortization of interest rate contracts	4,368						3,759	609
Reallocation of noncontrolling interest				16,986				(16,986)
Equity, value at Sep. 30, 2017	$ 8,099,695	$ 1,543	$ 200,000	$ 6,370,932	$ (692,739)	$ (2,722)	$ (51,796)	$ 2,274,477
Equity, shares at Sep. 30, 2017	154,322,266	154,322,000