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]	Noncontrolling interest - property partnerships [Member]
Equity, shares at Dec. 31, 2018		154,458,000
Equity, value at Dec. 31, 2018	$ 8,213,968	$ 1,545	$ 200,000	$ 6,407,623	$ (675,534)	$ (2,722)	$ (47,741)	$ 619,352	$ 1,711,445
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	(4,379)				(3,864)			(445)	(70)
Redemption of operating partnership units to common stock, shares		14,000
Redemption of operating partnership units to common stock, value	0	$ 0		492				(492)
Allocated net income for the year	131,159				100,730			11,599	18,830
Dividends/distributions declared	166,600				(149,415)			(17,185)
Shares issued pursuant to stock purchase plan, shares		4,000
Shares issued pursuant to stock purchase plan, value	373			373
Net activity from stock option and incentive plan, shares		39,000
Net activity from stock option and incentive plan, value	16,469			3,059				13,410
Contributions from noncontrolling interests in property partnerships	4,387								4,387
Distributions to noncontrolling interests in property partnerships	(24,128)								(24,128)
Effective portion of interest rate contracts	(2,628)						(2,359)	(269)	0
Amortization of interest rate contracts	1,666						1,366	156	144
Reallocation of noncontrolling interest				3,065				(3,065)
Equity, shares at Mar. 31, 2019		154,515,000
Equity, value at Mar. 31, 2019	$ 8,170,287	$ 1,545	200,000	6,414,612	(728,083)	(2,722)	(48,734)	623,061	1,710,608
Equity, shares at Dec. 31, 2019	154,790,298	154,790,000
Equity, value at Dec. 31, 2019	$ 8,014,236	$ 1,548	200,000	6,294,719	(760,523)	(2,722)	(48,335)	600,860	1,728,689
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	(1,679)				(1,505)			(174)	0
Redemption of operating partnership units to common stock, shares		462,000
Redemption of operating partnership units to common stock, value	0	$ 5		15,490				(15,495)
Allocated net income for the year	577,146				500,121			57,539	19,486
Dividends/distributions declared	(172,277)				(154,833)			(17,444)
Shares issued pursuant to stock purchase plan, shares		2,000
Shares issued pursuant to stock purchase plan, value	325			325
Net activity from stock option and incentive plan, shares		61,000
Net activity from stock option and incentive plan, value	23,060	$ 0		7,383				15,677
Contributions from noncontrolling interests in property partnerships	3,876								3,876
Distributions to noncontrolling interests in property partnerships	(15,750)								(15,750)
Effective portion of interest rate contracts	(9,720)						(8,732)	(988)	0
Amortization of interest rate contracts	1,666						1,367	155	144
Reallocation of noncontrolling interest	$ 0			3,558				(3,558)
Equity, shares at Mar. 31, 2020	155,314,555	155,315,000
Equity, value at Mar. 31, 2020	$ 8,420,883	$ 1,553	$ 200,000	$ 6,321,475	$ (416,740)	$ (2,722)	$ (55,700)	$ 636,572	$ 1,736,445