Related Party Arrangements - Distribution Support Agreement (Narrative) (Details) - USD ($)			12 Months Ended		33 Months Ended
	Dec. 23, 2015	Mar. 28, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Related Party Transaction [Line Items]
Common stock purchased			$ 7,697,289	$ 1,981,000
Class A common
Related Party Transaction [Line Items]
Common stock purchased (shares)			501,000	220,000	721,000
Common stock purchased		$ 200,000	$ 5,007,000	$ 2,000,000	$ 7,007,000
Class A common | Distribution Support Agreement
Related Party Transaction [Line Items]
Common stock purchased			$ 8,267
NorthStar Realty | Class A common | Distribution Support Agreement
Related Party Transaction [Line Items]
Commitment to purchase common stock (percent)			75.00%
Commitment to purchase common stock			$ 10,000,000		$ 10,000,000
Common stock purchased (shares)	164,835		682
Common stock purchased	$ 1,500,000
RXR Realty | Class A common | Distribution Support Agreement
Related Party Transaction [Line Items]
Commitment to purchase common stock (percent)			25.00%
Common stock purchased (shares)	54,945		227
Common stock purchased	$ 500,000