Real Estate Investments - Co-Investments (Details)	1 Months Ended				12 Months Ended
	Dec. 31, 2019 USD ($)	Nov. 30, 2019 USD ($) apartment	Oct. 31, 2019 USD ($) apartment	Aug. 31, 2019 USD ($) apartment	Dec. 31, 2019 USD ($) unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 01, 2019	Aug. 01, 2019
Business Acquisition [Line Items]
Promote interest earned				$ 52,200,000
Number of units acquired | unit					849
Purchase price					$ 373,300,000	$ 35,400,000
Debt assumed in connection with acquisition					143,006,000	45,804,000	$ 51,882,000
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	$ 1,335,339,000				1,335,339,000	1,300,140,000
Membership Combined Balance Sheets [Abstract]
Rental properties and real estate under development	546,075,000				546,075,000	454,629,000
Other liabilities	36,565,000				36,565,000	33,375,000
Membership Combined Statements Of Income [Abstract]
Interest expense					(217,339,000)	(220,492,000)	(222,894,000)
General and administrative					(54,262,000)	(53,451,000)	(41,385,000)
Equity income from co-investments					112,136,000	89,132,000	86,445,000
Investments with Related Parties
Membership Combined Statements Of Income [Abstract]
Equity income from co-investments					$ 7,500,000	2,000,000.0	1,900,000
BEX IV
Business Acquisition [Line Items]
Ownership percentage				50.10%
Debt assumed in connection with acquisition	44,400,000
BEX IV, LLC (BEX IV), Menlo Park
Business Acquisition [Line Items]
Number of units acquired | apartment				195
Purchase price				$ 148,000,000.0
Debt assumed in connection with acquisition				$ 44,400,000
Wesco V, LLC (Wesco V), Emeryville
Business Acquisition [Line Items]
Number of units acquired | apartment				331
Purchase price				$ 178,000,000.0
Debt assumed in connection with acquisition	89,000,000.0			$ 89,000,000.0
Canadian Pension Plan Investment Board (CPPIB or CPP), San Francisco, CA
Business Acquisition [Line Items]
Ownership percentage			55.00%
Number of units acquired | apartment			463
Gain on sale of properties			$ 50,200,000
Canadian Pension Plan Investment Board (CPPIB or CPP), San Francisco, CA | Rental and Other Property
Business Acquisition [Line Items]
Total property revenues			$ 311,000,000.0
Velo & Ray Apartments, Seattle, WA
Business Acquisition [Line Items]
Number of units acquired | apartment		308
Purchase price		$ 133,000,000.0
Debt assumed in connection with acquisition		$ 85,500,000
CPPIB
Business Acquisition [Line Items]
Ownership percentage					55.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	345,466,000				$ 345,466,000	482,507,000
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	216,756,000				$ 216,756,000	194,890,000
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	160,888,000				$ 160,888,000	121,780,000
Other
Business Acquisition [Line Items]
Ownership percentage					48.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	20,351,000				$ 20,351,000	34,093,000
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	743,461,000				$ 743,461,000	833,270,000
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	146,944,000				$ 146,944,000	94,060,000
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	444,934,000				444,934,000	372,810,000
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	73,200,000				73,200,000	51,800,000
Total Co Investment
Membership Combined Balance Sheets [Abstract]
Rental properties and real estate under development	4,733,762,000				4,733,762,000	4,367,987,000
Other assets	139,562,000				139,562,000	104,119,000
Total assets	4,873,324,000				4,873,324,000	4,472,106,000
Debt	2,442,213,000				2,442,213,000	2,190,764,000
Other liabilities	117,160,000				117,160,000	106,316,000
Equity	2,313,951,000				2,313,951,000	2,175,026,000
Total liabilities and equity	4,873,324,000				4,873,324,000	4,472,106,000
Company's share of equity	$ 1,335,339,000				1,335,339,000	1,300,140,000
Membership Combined Statements Of Income [Abstract]
Property revenues					336,922,000	332,164,000	312,841,000
Property operating expenses					(115,658,000)	(107,584,000)	(110,583,000)
Net operating income					221,264,000	224,580,000	202,258,000
Gain on sale of real estate					112,918,000	24,218,000	90,663,000
Interest expense					(65,665,000)	(63,913,000)	(62,844,000)
General and administrative					(9,575,000)	(6,379,000)	(9,091,000)
Depreciation and amortization					(121,006,000)	(126,485,000)	(118,048,000)
Net income					137,936,000	52,021,000	102,938,000
Company's share of net income					$ 112,136,000	$ 89,132,000	$ 86,445,000
LIBOR Swap Rate | BEX IV
Business Acquisition [Line Items]
Interest rate percentage								3.23%
LIBOR Swap Rate | BEX IV, LLC (BEX IV), Menlo Park
Business Acquisition [Line Items]
Interest rate percentage									3.25%
LIBOR Swap Rate | Wesco V, LLC (Wesco V), Emeryville
Business Acquisition [Line Items]
Interest rate percentage								1.30%	1.30%
LIBOR Swap Rate | Velo & Ray Apartments, Seattle, WA
Business Acquisition [Line Items]
Interest rate percentage		1.30%