Co-investments - Summary of Investments (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 1,088,332	$ 1,161,275
Total operating and other co-investments, net [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	777,209	781,905
Membership Interest In CPPIB [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 502,419	422,068
Weighted Average Essex Ownership Percentage	54.00%
Membership interest in Wesco I, III, IV, and V [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 225,041	180,687
Weighted Average Essex Ownership Percentage	50.00%
Membership Interest In Palm Valley [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 0	68,396
Weighted Average Essex Ownership Percentage	50.00%
Membership interest in BEXAEW [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 45,523	47,963
Weighted Average Essex Ownership Percentage	50.00%
BEX II [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ (36,245)	19,078
Weighted Average Essex Ownership Percentage	50.00%
Membership In Other [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 40,471	43,713
Weighted Average Essex Ownership Percentage	53.00%
Total development co-investments, net [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 85,670	157,317
Weighted Average Essex Ownership Percentage	50.00%
Total preferred interest co-investments [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 225,453	222,053
Total preferred interest co-investments [Member] | Investments in Majority-owned Subsidiaries [Member]
Schedule of Equity Method Investments [Line Items]
Co-investments	$ 20,700	$ 35,900