Real Estate Investments - Co-Investments (Details) $ in Thousands	1 Months Ended				12 Months Ended
	Dec. 31, 2016 USD ($) unit	Nov. 30, 2016 USD ($) property	Aug. 31, 2015 USD ($)	Mar. 31, 2015 USD ($) community	Dec. 31, 2016 USD ($) community unit	Dec. 31, 2015 USD ($) community unit	Dec. 31, 2014 USD ($) community unit	Dec. 31, 2010
Business Acquisition [Line Items]
Gain on disposal of equity method investment			$ 1,500		$ 13,046	$ 0	$ 6,558
Ownership Percentage								3.00%
Co-investment	$ 1,161,275		$ 20,400	$ 13,700	1,161,275	1,036,047
Real estate under development	190,505				190,505	242,326
Other liabilities	32,922				32,922	34,518
Gain on sale of real estate				$ 2,400	14,000	44,900	43,600
Interest expense					(219,654)	(204,827)	(164,551)
General and administrative					(40,751)	(40,090)	(40,878)
Equity income in co-investments					$ 48,698	$ 21,861	$ 39,893
Number of communities sold | community				2	3	2	4
Number of units sold | unit					323	848	594
Sales Price				$ 13,000	$ 80,800	$ 308,800	$ 120,400
Investments With Related Parties [Member]
Business Acquisition [Line Items]
Equity income in co-investments					3,400	3,700
BEXAWE, LLC [Member]
Business Acquisition [Line Items]
Gain on sale of real estate					$ 13,000
Number of communities sold | community					2
Number of units sold | unit					532
Sales Price					$ 147,300
Preferred Interest In A Limited Liability Company That Owns An Apartment Development In San Jose With A Preferred Return Of Nine Percent [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage		50.10%
Co-investment		$ 12,900
Total operating co investments [Member]
Business Acquisition [Line Items]
Co-investment	$ 781,905				$ 781,905	$ 831,521
Number of apartments owned through joint ventures | unit	11,274				11,274	10,520
Total operating co investments [Member] | Minimum [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage	50.00%				50.00%
Total operating co investments [Member] | Maximum [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage	55.00%				55.00%
BEX II [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage	49.90%				49.90%
Number of properties contributed into new entity | property		4
Gain on disposal of equity method investment	$ 126,600
Ownership Percentage					50.00%
Co-investment	19,078				$ 19,078	$ 0
CPPIB [Member]
Business Acquisition [Line Items]
Co-investment	422,068				$ 422,068	422,317
CPPIB [Member] | Minimum [Member]
Business Acquisition [Line Items]
Ownership Percentage					50.00%
CPPIB [Member] | Maximum [Member]
Business Acquisition [Line Items]
Ownership Percentage					55.00%
Wesco I, III, and IV [Member]
Business Acquisition [Line Items]
Ownership Percentage					50.00%
Co-investment	180,687				$ 180,687	218,902
Palm Valley [Member]
Business Acquisition [Line Items]
Ownership Percentage					50.00%
Co-investment	68,396				$ 68,396	68,525
BEXAEW [Member]
Business Acquisition [Line Items]
Ownership Percentage					50.00%
Co-investment	47,963				$ 47,963	88,850
Other [Member]
Business Acquisition [Line Items]
Co-investment	43,713				$ 43,713	32,927
Other [Member] | Minimum [Member]
Business Acquisition [Line Items]
Ownership Percentage					50.00%
Other [Member] | Maximum [Member]
Business Acquisition [Line Items]
Ownership Percentage					55.00%
Total development co investments [Member]
Business Acquisition [Line Items]
Co-investment	$ 157,317				$ 157,317	$ 98,214
Number of apartments owned through joint ventures | unit	1,427				1,427	1,676
Total development co investments [Member] | Minimum [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage	50.00%				50.00%
Ownership Percentage					50.00%
Total development co investments [Member] | Maximum [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage	55.00%				55.00%
Ownership Percentage					55.00%
Total preferred interest investments [Member]
Business Acquisition [Line Items]
Co-investment	$ 222,053				$ 222,053	$ 106,312
Total preferred interest investments [Member] | Investments in Majority-owned Subsidiaries [Member]
Business Acquisition [Line Items]
Co-investment	35,900				35,900	35,800
Total co investment [Member]
Business Acquisition [Line Items]
Real estate under development	3,807,245				3,807,245	3,360,360
Other assets	121,505				121,505	96,785
Total assets	3,928,750				3,928,750	3,457,145
Debt	1,617,639				1,617,639	1,499,601
Other liabilities	74,607				74,607	92,241
Equity	2,236,504				2,236,504	1,865,303
Total liabilities and equity	3,928,750				3,928,750	3,457,145
Company's share of equity	$ 1,161,275				1,161,275	1,036,047
Property revenues					289,011	260,175	188,548
Property operating expenses					(99,637)	(93,067)	(71,419)
Net operating income					189,374	167,108	117,129
Gain on sale of real estate					28,291	14	23,333
Interest expense					(46,894)	(44,834)	(39,990)
General and administrative					(7,448)	(5,879)	(6,321)
Equity income in co-investments					0	0	26,798
Depreciation and amortization					(103,986)	(103,613)	(74,657)
Net income					59,337	12,796	46,292
Company's share of net income					$ 48,698	$ 21,861	$ 39,893