Real Estate Investments - Co-Investments (Details) $ in Thousands	1 Months Ended				12 Months Ended
	Dec. 31, 2018 USD ($) unit	Nov. 30, 2018 USD ($) unit	Oct. 31, 2018 USD ($) unit	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) unit	Dec. 31, 2017 USD ($) unit	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Promote interest earned				$ 20,500
Number of units acquired | unit					166
Acquisitions of real estate and acquisition related capital expenditures					$ 15,311	$ 206,194	$ 315,632
Revenues					1,400,053	1,363,899	1,294,001
Purchase Price					35,400
Gain on remeasurement of co-investment					1,253	88,641	0
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	$ 1,300,140				1,300,140	1,119,258
Membership Combined Balance Sheets [Abstract]
Rental properties and real estate under development	454,629				454,629	355,735
Other liabilities	$ 33,375				33,375	33,132
Membership Combined Statements Of Income [Abstract]
Interest expense					(220,492)	(222,894)	(219,654)
General and administrative					(53,451)	(41,385)	(40,751)
Equity income from co-investments					89,132	86,445	48,698
Investments With Related Parties [Member]
Membership Combined Statements Of Income [Abstract]
Equity income from co-investments					2,000	1,900	3,400
Rental and other property [Member]
Business Acquisition [Line Items]
Revenues					$ 1,390,870	1,354,325	1,285,723
Meridian At Midtown [Member] | Wesco V [Member]
Business Acquisition [Line Items]
Number of units acquired | unit			218
Acquisitions of real estate and acquisition related capital expenditures			$ 104,000
Mortgage debt assumed			$ 69,900
Effective interest rate of mortgage debt assumed			4.50%
Enclave At Town Square [Member] | BEXAWE, LLC [Member]
Business Acquisition [Line Items]
Number of units sold | unit		124
Gain on sale of properties		$ 5,400
Repayments of debt		16,100
Enclave At Town Square [Member] | BEXAWE, LLC [Member] | Rental and other property [Member]
Business Acquisition [Line Items]
Revenues		$ 30,500
The Summit [Member] | Wesco III [Member]
Business Acquisition [Line Items]
Number of units sold | unit		125
Gain on sale of properties		$ 5,200
Repayments of debt		15,600
The Summit [Member] | Wesco III [Member] | Rental and other property [Member]
Business Acquisition [Line Items]
Revenues		34,800
Marquis [Member]
Business Acquisition [Line Items]
Ownership Percentage	49.90%
Purchase Price	$ 35,400
Encumberance of mortgage debt		$ 45,800
Number of units in real estate property | unit	166				166
Gain on remeasurement of co-investment	$ 1,300
Total operating co investments [Member]
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	$ 833,270				$ 833,270	$ 780,332
Membership Combined Statements Of Income [Abstract]
Number of apartments owned through joint ventures | unit	10,613				10,613	10,810
CPPIB [Member]
Business Acquisition [Line Items]
Ownership Percentage					54.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	$ 482,507				$ 482,507	$ 500,287
Wesco I, III, IV and V [Member]
Business Acquisition [Line Items]
Ownership Percentage					52.00%
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	194,890				$ 194,890	214,408
BEXAEW, BEXII and BEX III [Member]
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	121,780				$ 121,780	13,827
BEX II [Member]
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	(36,700)				$ (36,700)
Other [Member]
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	34,093				$ 34,093	51,810
Total development co investments [Member]
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	$ 94,060				$ 94,060	$ 73,770
Membership Combined Statements Of Income [Abstract]
Number of apartments owned through joint ventures | unit	814				814	814
Total preferred interest investments [Member]
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	$ 372,810				$ 372,810	$ 265,156
Total preferred interest investments [Member] | Investments in Majority-owned Subsidiaries [Member]
Business Acquisition [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures	51,800				51,800	15,700
Total co investment [Member]
Membership Combined Balance Sheets [Abstract]
Rental properties and real estate under development	4,367,987				4,367,987	3,722,778
Other assets	104,119				104,119	110,333
Total assets	4,472,106				4,472,106	3,833,111
Debt	2,190,764				2,190,764	1,705,051
Other liabilities	106,316				106,316	45,515
Equity	2,175,026				2,175,026	2,082,545
Total liabilities and equity	4,472,106				4,472,106	3,833,111
Company's share of equity	$ 1,300,140				1,300,140	1,155,984
Membership Combined Statements Of Income [Abstract]
Property revenues					332,164	312,841	289,011
Property operating expenses					(107,584)	(110,583)	(99,637)
Net operating income					224,580	202,258	189,374
Gain on sale of real estate					24,218	90,663	28,291
Interest expense					(63,913)	(62,844)	(46,894)
General and administrative					(6,379)	(9,091)	(7,448)
Depreciation and amortization					(126,485)	(118,048)	(103,986)
Net income					52,021	102,938	59,337
Company's share of net income					$ 89,132	$ 86,445	$ 48,698