Consolidated Statements Of Stockholders' Equity - USD ($)	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 - Common units [Member]	Noncontrolling interest - property partnerships [Member]
Equity, value at Dec. 31, 2017	$ 8,102,456,000	$ 1,543,000	$ 200,000,000	$ 6,377,908,000	$ (712,343,000)	$ (2,722,000)	$ (50,429,000)	$ 604,739,000	$ 1,683,760,000
Equity, shares at Dec. 31, 2017		154,325,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	5,496,000				4,933,000			563,000
Redemption of operating partnership units to Common Stock, shares		60,000
Redemption of operating partnership units to Common Stock, value	0	$ 1,000		2,111,000				(2,112,000)
Allocated net income for the year	527,322,000				431,710,000			49,128,000	46,484,000
Dividends/distributions declared	(447,342,000)				(401,612,000)			(45,730,000)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	797,000			797,000
Net activity from stock option and incentive plan, shares		49,000
Net activity from stock option and incentive plan, value	30,570,000			1,354,000				29,216,000
Contributions from noncontrolling interests in property partnerships	37,148,000								37,148,000
Distributions to noncontrolling interests in property partnerships	(56,796,000)								(56,796,000)
Effective portion of interest rate contracts	1,325,000						1,190,000	135,000	0
Amortization of interest rate contracts	4,998,000						4,102,000	464,000	432,000
Reallocation of noncontrolling interest	0			18,023,000				(18,023,000)
Equity, value at Sep. 30, 2018	8,205,974,000	$ 1,544,000	200,000,000	6,400,193,000	(677,312,000)	(2,722,000)	(45,137,000)	618,380,000	1,711,028,000
Equity, shares at Sep. 30, 2018		154,440,000
Equity, value at Jun. 30, 2018	8,213,242,000	$ 1,544,000	200,000,000	6,391,460,000	(649,747,000)	(2,722,000)	(47,695,000)	621,221,000	1,699,181,000
Equity, shares at Jun. 30, 2018		154,412,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemption of operating partnership units to Common Stock, shares		25,000
Redemption of operating partnership units to Common Stock, value	0	$ 0		916,000				(916,000)
Allocated net income for the year	150,445,000				121,778,000			13,817,000	14,850,000
Dividends/distributions declared	(166,365,000)				(149,343,000)			(17,022,000)
Shares issued pursuant to stock purchase plan, shares		3,000
Shares issued pursuant to stock purchase plan, value	368,000			368,000
Net activity from stock option and incentive plan, shares		0
Net activity from stock option and incentive plan, value	8,440,000			754,000				7,686,000
Contributions from noncontrolling interests in property partnerships	9,616,000								9,616,000
Distributions to noncontrolling interests in property partnerships	(12,763,000)								(12,763,000)
Effective portion of interest rate contracts	1,325,000						1,190,000	135,000
Amortization of interest rate contracts	1,666,000						1,368,000	154,000	144,000
Reallocation of noncontrolling interest	0			6,695,000				(6,695,000)
Equity, value at Sep. 30, 2018	8,205,974,000	$ 1,544,000	200,000,000	6,400,193,000	(677,312,000)	(2,722,000)	(45,137,000)	618,380,000	1,711,028,000
Equity, shares at Sep. 30, 2018		154,440,000
Equity, value at Dec. 31, 2018	$ 8,213,968,000	$ 1,545,000	200,000,000	6,407,623,000	(675,534,000)	(2,722,000)	(47,741,000)	619,352,000	1,711,445,000
Equity, shares at Dec. 31, 2018	154,458,478	154,458,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle	$ (4,379,000)				(3,864,000)			(445,000)	(70,000)
Redemption of operating partnership units to Common Stock, shares		42,000
Redemption of operating partnership units to Common Stock, value	0	$ 1,000		1,434,000				(1,435,000)
Allocated net income for the year	475,990,000				378,075,000			43,133,000	54,782,000
Dividends/distributions declared	(499,934,000)				(448,343,000)			(51,591,000)
Shares issued pursuant to stock purchase plan, shares		6,000
Shares issued pursuant to stock purchase plan, value	688,000			688,000
Net activity from stock option and incentive plan, shares		66,000
Net activity from stock option and incentive plan, value	26,887,000			(2,665,000)				29,552,000
sale of an interest in property partnerships	0			(4,216,000)					4,216,000
Acquisition of noncontrolling interest in property partnership	(186,963,000)			(162,462,000)					(24,501,000)
Contributions from noncontrolling interests in property partnerships	26,968,000								26,968,000
Distributions to noncontrolling interests in property partnerships	(53,149,000)								(53,149,000)
Effective portion of interest rate contracts	(9,307,000)						(8,354,000)	(953,000)
Amortization of interest rate contracts	4,998,000						4,099,000	467,000	432,000
Reallocation of noncontrolling interest	0			34,390,000				(34,390,000)
Equity, value at Sep. 30, 2019	$ 7,995,767,000	$ 1,546,000	200,000,000	6,274,792,000	(749,666,000)	(2,722,000)	(51,996,000)	603,690,000	1,720,123,000
Equity, shares at Sep. 30, 2019	154,572,073	154,572,000
Equity, value at Jun. 30, 2019	$ 8,020,667,000	$ 1,546,000	200,000,000	6,278,961,000	(710,592,000)	(2,722,000)	(51,340,000)	608,593,000	1,696,221,000
Equity, shares at Jun. 30, 2019		154,563,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle									0
Redemption of operating partnership units to Common Stock, shares		7,000
Redemption of operating partnership units to Common Stock, value	0	$ 0		223,000				(223,000)
Allocated net income for the year	141,370,000				110,394,000			12,506,000	18,470,000
Dividends/distributions declared	(166,668,000)				(149,468,000)			(17,200,000)
Shares issued pursuant to stock purchase plan, shares		2,000
Shares issued pursuant to stock purchase plan, value	315,000			315,000
Net activity from stock option and incentive plan, shares		0
Net activity from stock option and incentive plan, value	(445,000)			(7,219,000)				6,774,000
sale of an interest in property partnerships	0			(4,216,000)					4,216,000
Acquisition of noncontrolling interest in property partnership	43,000			43,000
Contributions from noncontrolling interests in property partnerships	14,820,000								14,820,000
Distributions to noncontrolling interests in property partnerships	(13,748,000)								(13,748,000)
Effective portion of interest rate contracts	(2,253,000)						(2,022,000)	(231,000)
Amortization of interest rate contracts	1,666,000						1,366,000	156,000	144,000
Reallocation of noncontrolling interest	0			6,685,000				(6,685,000)
Equity, value at Sep. 30, 2019	$ 7,995,767,000	$ 1,546,000	$ 200,000,000	$ 6,274,792,000	$ (749,666,000)	$ (2,722,000)	$ (51,996,000)	$ 603,690,000	$ 1,720,123,000
Equity, shares at Sep. 30, 2019	154,572,073	154,572,000