Co-investments - Combined Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Rental properties and real estate under development	$ 212,426		$ 212,426			$ 386,047
Total assets	12,788,641		12,788,641			12,936,177
Debt	6,624,044		6,624,044			6,720,746
Other liabilities	38,946		38,946			39,140
Equity	6,131,899	$ 6,267,482	6,131,899	$ 6,267,482	$ 6,136,703	6,183,192	$ 6,352,881	$ 6,403,504
Total liabilities and equity/capital	12,788,641		12,788,641			12,936,177
Equity Method Investment, Summarized Financial Information [Abstract]
Property revenues	362,857	370,811	1,068,960	1,133,675
Interest expense	(50,019)	(55,430)	(152,639)	(165,024)
General and administrative	(12,712)	(13,310)	(34,746)	(42,244)
Net income (loss)	125,002	78,842	371,566	497,683
Total co-investment | Affiliated Entity
Equity Method Investment, Summarized Financial Information [Abstract]
Company's share of net income	2,400	2,200	7,000	6,400
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Total co-investment
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Rental properties and real estate under development	4,216,981		4,216,981			4,242,611
Other assets	228,721		228,721			200,777
Total assets	4,445,702		4,445,702			4,443,388
Debt	2,705,882		2,705,882			2,611,365
Other liabilities	221,022		221,022			189,515
Equity	1,518,798		1,518,798			1,642,508
Total liabilities and equity/capital	4,445,702		4,445,702			4,443,388
Company's share of equity	1,052,824		1,052,824			$ 1,018,010
Equity Method Investment, Summarized Financial Information [Abstract]
Property revenues	71,195	76,581	211,359	226,125
Property operating expenses	(27,588)	(28,047)	(81,932)	(79,621)
Net operating income	43,607	48,534	129,427	146,504
Interest expense	(15,347)	(19,369)	(48,012)	(59,700)
General and administrative	(3,331)	(5,161)	(11,641)	(12,636)
Depreciation and amortization	(32,290)	(29,732)	(96,812)	(86,947)
Net income (loss)	(7,361)	(5,728)	(27,038)	(12,779)
Company's share of net income	$ 25,433	$ 14,960	$ 60,692	$ 53,514