Real Estate Investments - Co-Investments (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2020 community apartment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) community apartment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 1,018,010	$ 1,335,339
Membership Combined Balance Sheets [Abstract]
Rental properties and real estate under development		386,047	546,075
Total assets		12,936,177	12,705,405
Debt		6,720,746	6,264,491
Other liabilities		39,140	36,565
Equity		6,183,192	6,403,504	$ 6,393,844	$ 6,396,825
Total liabilities and equity/capital		12,936,177	12,705,405
Membership Combined Statements Of Income [Abstract]
Revenues		1,495,748	1,460,155	1,400,053
Interest expense		(220,633)	(217,339)	(220,492)
General and administrative		(65,388)	(54,262)	(53,451)
Net income		599,332	464,448	413,599
Equity income from co-investments		66,512	$ 112,136	89,132
Apartment Building
Business Acquisition [Line Items]
Number of communities held by acquired investment | community			4
Number of units held by acquired investment | apartment			849
Total Co Investment
Membership Combined Balance Sheets [Abstract]
Rental properties and real estate under development		4,242,611	$ 4,733,762
Other assets		200,777	139,562
Total assets		4,443,388	4,873,324
Debt		2,611,365	2,442,213
Other liabilities		189,515	117,160
Equity		1,642,508	2,313,951
Total liabilities and equity/capital		4,443,388	4,873,324
Company's share of equity		1,018,010	1,335,339
Membership Combined Statements Of Income [Abstract]
Revenues		300,624	336,922	332,164
Property operating expenses		(108,682)	(115,658)	(107,584)
Net operating income		191,942	221,264	224,580
Gain on sale of real estate		0	112,918	24,218
Interest expense		(78,962)	(65,665)	(63,913)
General and administrative		(17,079)	(9,575)	(6,379)
Depreciation and amortization		(117,836)	(121,006)	(126,485)
Net income		(21,935)	137,936	52,021
Company's share of net income		66,512	112,136	89,132
Investments with Related Parties
Membership Combined Statements Of Income [Abstract]
Equity income from co-investments		$ 8,600	7,500	$ 2,000
CPPIB
Business Acquisition [Line Items]
Ownership percentage		0.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 0	345,466
Wesco I, III, IV and V
Business Acquisition [Line Items]
Ownership percentage		51.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 178,322	216,756
BEXAEW, BEX II, BEX III, and BEX IV
Business Acquisition [Line Items]
Ownership percentage		50.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 152,309	160,888
Other
Business Acquisition [Line Items]
Ownership percentage		47.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 27,635	20,351
Total Operating Co-investments
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 358,266	743,461
Total Development Co-Investments
Business Acquisition [Line Items]
Ownership percentage		50.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 157,433	146,944
Total Preferred Interest Investments
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		502,311	444,934
Total Preferred Interest Investments | Investments in Majority-Owned Subsidiaries
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 81,400	$ 73,200
CPPIB Interest
Business Acquisition [Line Items]
Investment interest acquired	45.00%
CPPIB Interest | Apartment Building
Business Acquisition [Line Items]
Number of communities held by acquired investment | community	6
Number of units held by acquired investment | apartment	2,020