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 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		66,000
Conversion of operating partnership units to Common Stock, value	0	$ 1		2,240				(2,241)
Conversions of redeemable preferred units to common units	33,306							33,306
Allocated net income for the year	156,249				135,801			20,448
Dividends/distributions declared	(226,851)				(204,178)
Dividends/distributions declared								(22,673)
Shares issued pursuant to stock purchase plan, shares		4,000
Shares issued pursuant to stock purchase plan, value	357			357
Net activity from stock option and incentive plan, shares		40,000
Net activity from stock option and incentive plan, value	16,442	$ 0		3,543				12,899
Contributions from noncontrolling interests in property partnerships	1,675							1,675
Distributions to noncontrolling interests in property partnerships	(12,149)							(12,149)
Amortization of interest rate contracts	1,253						1,127	126
Reallocation of noncontrolling interest	0			10,985				(10,985)
Equity, value at Jun. 30, 2014	7,013,900	$ 1,531	200,000	5,679,578	(176,929)	(2,722)	(10,429)	1,322,871
Equity, shares at Jun. 30, 2014		153,093,000
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		322,000
Conversion of operating partnership units to Common Stock, value		$ 4		10,839				(10,843)
Conversions of redeemable preferred units to common units	$ 0
Allocated net income for the year	305,462				255,901			49,561
Dividends/distributions declared	(228,254)				(204,676)
Dividends/distributions declared								(23,578)
Shares issued pursuant to stock purchase plan, shares		2,000
Shares issued pursuant to stock purchase plan, value	313			313
Net activity from stock option and incentive plan, shares		36,000
Net activity from stock option and incentive plan, value	27,562			3,407				24,155
Contributions from noncontrolling interests in property partnerships	1,089							1,089
Distributions to noncontrolling interests in property partnerships	(34,022)							(34,022)
Effective portion of interest rate contracts	12,106						10,027	2,079
Amortization of interest rate contracts	1,255						1,125	130
Reallocation of noncontrolling interest				8,740				(8,740)
Equity, value at Jun. 30, 2015	$ 7,988,447	$ 1,535	$ 200,000	$ 6,293,556	$ (711,239)	$ (2,722)	$ 1,848	$ 2,205,469
Equity, shares at Jun. 30, 2015	153,473,931	153,474,000