Real Estate Investments - Development Co-Investments (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2018 USD ($)	Dec. 31, 2017 USD ($) unit	Dec. 31, 2018 USD ($) unit	Dec. 31, 2015 USD ($) unit
Real Estate Properties [Line Items]
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 1,119,258	$ 1,300,140
Number of units to be developed | unit			1,861
Commitment to fund preferred equity investment in the project	$ 12,500	$ 153,800
Annualized preferred return rate	9.90%
Total development co investments [Member]
Real Estate Properties [Line Items]
Number of apartments owned through joint ventures | unit		814	814
Investments in (distributions in excess of investments in) and advance to affiliates, subsidiaries, associates and joint ventures		$ 73,770	$ 94,060
Ohlone Multi-family Community [Member]
Real Estate Properties [Line Items]
Number of units to be developed | unit		269
Equity method investment, ownership percentage		50.00%
Estimated cost active development projects		$ 136,000
Commitment to fund preferred equity investment in the project		$ 28,900
Annualized preferred return rate		10.00%
Folsom 500 [Member]
Real Estate Properties [Line Items]
Number of units to be developed | unit				545
Equity method investment, ownership percentage				50.00%
Estimated cost active development projects				$ 415,000