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, 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		153,790,000
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	0	$ 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	$ 0		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	0			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		154,322,000
Equity, value at Dec. 31, 2017	$ 8,102,456	$ 1,543	200,000	6,377,908	(712,343)	(2,722)	(50,429)	2,288,499
Equity, shares at Dec. 31, 2017	154,325,286	154,325,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units to Common Stock, shares		60,000
Conversion of operating partnership units to Common Stock, value		$ 1		2,111				(2,112)
Allocated net income for the year	$ 527,322				431,710			95,612
Dividends/distributions declared	(447,342)				(401,612)			(45,730)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	797			797
Net activity from stock option and incentive plan, shares		49,000
Net activity from stock option and incentive plan, value	30,570			1,354				29,216
Cumulative effect of a change in accounting principle	5,496				4,933			563
Contributions from noncontrolling interests in property partnerships	37,148							37,148
Distributions to noncontrolling interests in property partnerships	(56,796)							(56,796)
Effective portion of interest rate contracts	1,325						1,190	135
Amortization of interest rate contracts	4,998						4,102	896
Reallocation of noncontrolling interest				18,023				(18,023)
Equity, value at Sep. 30, 2018	$ 8,205,974	$ 1,544	$ 200,000	$ 6,400,193	$ (677,312)	$ (2,722)	$ (45,137)	$ 2,329,408
Equity, shares at Sep. 30, 2018	154,440,239	154,440,000