Co-investments - Combined Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Rental properties and real estate under development	$ 208,330		$ 208,330			$ 386,047
Total assets	12,747,199		12,747,199			12,936,177
Debt	6,575,470		6,575,470			6,720,746
Other liabilities	38,068		38,068			39,140
Equity	6,136,703	$ 6,352,881	6,136,703	$ 6,352,881	$ 6,210,931	6,183,192	$ 6,417,949	$ 6,403,504
Total liabilities and equity/capital	12,747,199		12,747,199			12,936,177
Equity Method Investment, Summarized Financial Information [Abstract]
Property revenues	350,978	370,497	706,103	762,864
Interest expense	(50,971)	(54,447)	(102,620)	(109,594)
General and administrative	(12,222)	(14,952)	(22,034)	(28,934)
Net income	69,615	90,076	246,564	418,841
Total co-investment | Affiliated Entity
Equity Method Investment, Summarized Financial Information [Abstract]
Company's share of net income	2,300	2,100	4,600	4,200
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	4,082,553		4,082,553			4,242,611
Other assets	225,482		225,482			200,777
Total assets	4,308,035		4,308,035			4,443,388
Debt	2,529,501		2,529,501			2,611,365
Other liabilities	195,048		195,048			189,515
Equity	1,583,486		1,583,486			1,642,508
Total liabilities and equity/capital	4,308,035		4,308,035			4,443,388
Company's share of equity	1,037,270		1,037,270			$ 1,018,010
Equity Method Investment, Summarized Financial Information [Abstract]
Property revenues	68,405	72,175	140,164	149,544
Property operating expenses	(27,013)	(25,859)	(54,344)	(51,574)
Net operating income	41,392	46,316	85,820	97,970
Interest expense	(15,965)	(19,478)	(32,665)	(40,331)
General and administrative	(4,029)	(3,392)	(8,310)	(7,475)
Depreciation and amortization	(31,813)	(28,778)	(64,522)	(57,215)
Net income	(10,415)	(5,332)	(19,677)	(7,051)
Company's share of net income	$ 18,248	$ 17,257	$ 35,259	$ 38,554