Real Estate Investments Co-Investments (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) apartment	Dec. 31, 2014 USD ($) apartment	Dec. 31, 2013 USD ($)	Dec. 31, 2010	Aug. 31, 2015 USD ($)
Business Acquisition [Line Items]
Ownership Percentage					3.00%
Co-investment	$ 13,700	$ 1,036,047	$ 1,042,423			$ 20,400
Real estate under development		242,326	429,096
Other liabilities		34,518	32,444
Gain on sale of real estate	$ 2,400	44,900	43,600	$ 29,200
Interest expense		(204,827)	(164,551)	(116,524)
General and administrative		(40,090)	(40,878)	(26,684)
Equity income from co-investments		21,861	39,893	55,865
Investments With Related Parties [Member]
Business Acquisition [Line Items]
Equity income from co-investments		3,700	3,800
CPPIB [Member]
Business Acquisition [Line Items]
Co-investment		$ 329,723	336,977
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		$ 218,902	256,790
BEXAEW [Member]
Business Acquisition [Line Items]
Ownership Percentage		50.00%
Co-investment		$ 88,850	97,686
Palm Valley [Member]
Business Acquisition [Line Items]
Ownership Percentage		50.00%
Co-investment		$ 68,525	70,186
Other [Member]
Business Acquisition [Line Items]
Co-investment		$ 32,927	50,438
Other [Member] | Minimum [Member]
Business Acquisition [Line Items]
Ownership Percentage		28.00%
Other [Member] | Maximum [Member]
Business Acquisition [Line Items]
Ownership Percentage		55.00%
Total operating co investments [Member]
Business Acquisition [Line Items]
Co-investment		$ 738,927	$ 812,077
Number Of apartments owned through joint ventures | apartment		10,520	9,983
Total operating co investments [Member] | Minimum [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage		50.00%
Total operating co investments [Member] | Maximum [Member]
Business Acquisition [Line Items]
Equity method investment, ownership percentage		55.00%
Total development co investments [Member]
Business Acquisition [Line Items]
Co-investment		$ 190,808	$ 121,655
Number Of apartments owned through joint ventures | apartment		1,676	2,296
Total development co investments [Member] | Minimum [Member]
Business Acquisition [Line Items]
Ownership Percentage		50.00%
Equity method investment, ownership percentage		50.00%
Total development co investments [Member] | Maximum [Member]
Business Acquisition [Line Items]
Ownership Percentage		55.00%
Equity method investment, ownership percentage		55.00%
Total preferred interest investments [Member]
Business Acquisition [Line Items]
Co-investment		$ 106,312	$ 108,691
Total co investment [Member]
Business Acquisition [Line Items]
Real estate under development		3,360,360	3,426,574
Other assets		96,785	107,902
Total assets		3,457,145	3,534,476
Debt		1,499,601	1,568,398
Other liabilities		92,241	91,579
Equity		1,865,303	1,874,499
Total liabilities and equity		3,457,145	3,534,476
Company's share of equity		1,036,047	1,042,423
Property revenues		260,175	188,548	100,402
Property operating expenses		(93,067)	(71,419)	(37,518)
Net operating income		167,108	117,129	62,884
Gain on sale of real estate		14	23,333	146,758
Interest expense		(44,834)	(39,990)	(24,155)
General and administrative		(5,879)	(6,321)	(5,344)
Equity income from co-investments		0	26,798	18,703
Depreciation and amortization		(103,613)	(74,657)	(36,831)
Net income		12,796	46,292	162,015
Company's share of net income		$ 21,861	$ 39,893	$ 55,865