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		13,000
Conversion of operating partnership units to Common Stock, value	0	$ 0		446				(446)
Allocated net income for the year	216,222				184,365			31,857
Dividends/distributions declared	(114,326)				(102,461)			(11,865)
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		9,000
Net activity from stock option and incentive plan, value	9,080	$ 0		696				8,384
Contributions from noncontrolling interests in property partnerships	2,489							2,489
Distributions to noncontrolling interests in property partnerships	(12,915)							(12,915)
Effective portion of interest rate contracts	(58,646)						(43,154)	(15,492)
Amortization of interest rate contracts	627						562	65
Reallocation of noncontrolling interest	0			(438)				438
Equity, value at Mar. 31, 2016	7,929,790	$ 1,536	200,000	6,306,723	(699,048)	(2,722)	(56,706)	2,180,007
Equity, shares at Mar. 31, 2016		153,605,000
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		23,000
Conversion of operating partnership units to Common Stock, value		$ 0		793				(793)
Allocated net income for the year	$ 115,564				99,708			15,856
Dividends/distributions declared	(131,665)				(118,012)			(13,653)
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		33,000
Net activity from stock option and incentive plan, value	12,281			996				11,285
Cumulative effect of a change in accounting principle	(2,035)				(272)			(1,763)
Contributions from noncontrolling interests in property partnerships	8,145							8,145
Distributions to noncontrolling interests in property partnerships	(13,635)							(13,635)
Effective portion of interest rate contracts	180						97	83
Amortization of interest rate contracts	1,306						1,171	135
Reallocation of noncontrolling interest				4,384				(4,384)
Equity, value at Mar. 31, 2017	$ 7,922,438	$ 1,538	$ 200,000	$ 6,339,970	$ (712,270)	$ (2,722)	$ (50,983)	$ 2,146,905
Equity, shares at Mar. 31, 2017	153,849,231	153,849,000