Investments in Real Estate Entities - Financial Position and Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
ASSETS
Real estate, net	$ 18,300,316		$ 18,300,316		$ 18,432,989
Total assets	19,351,490		19,351,490		19,121,051
LIABILITIES AND EQUITY
Mortgage notes payable, net	931,772		931,772		937,642
Partners' capital	10,870,190		10,870,190		10,989,549
Total liabilities and equity	19,351,490		19,351,490		19,121,051
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	576,405	$ 577,263	1,178,056	$ 1,143,446
Operating and other expenses	(443,980)	(428,774)	(906,648)	(838,113)
Gain on sale of communities	35,295	20,530	59,731	35,365
Interest expense, net	(53,399)	(50,010)	(109,313)	(97,902)
Depreciation expense	(176,249)	(162,693)	(354,160)	(324,749)
Net income	170,869	168,305	338,875	338,723
Equity Method Investment, Net Income (Loss), Portion Attributable To Parent	1,041	730	2,746	202
Equity Method Investments, Amortization Of Excess Investment And Other	(529)	(533)	(1,059)	(1,065)
Equity in income (loss) of unconsolidated real estate entities	512	197	1,687	(863)
Equity Method Investment, Nonconsolidated Investee or Group of Investees
ASSETS
Real estate, net	1,203,277		1,203,277		1,204,470
Other assets	198,997		198,997		196,488
Total assets	1,402,274		1,402,274		1,400,958
LIABILITIES AND EQUITY
Mortgage notes payable, net	780,217		780,217		782,257
Other liabilities	154,881		154,881		157,379
Partners' capital	467,176		467,176		461,322
Total liabilities and equity	1,402,274		1,402,274		$ 1,400,958
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	30,427	35,998	63,499	71,253
Operating and other expenses	(11,732)	(13,885)	(23,912)	(28,089)
Gain on sale of communities	40	0	40	0
Interest expense, net	(8,053)	(8,543)	(16,109)	(17,096)
Depreciation expense	(8,713)	(18,346)	(17,402)	(40,042)
Net income	$ 1,969	$ (4,776)	$ 6,116	$ (13,974)