Subsequent Events - NorthStar Realty and RXR Purchase of Common Stock (Details) - USD ($)				12 Months Ended		33 Months Ended
	Mar. 16, 2017	Dec. 23, 2015	Mar. 28, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Subsequent Event [Line Items]
Common stock offering				$ 7,697,289	$ 1,981,000
Class A
Subsequent Event [Line Items]
Common stock purchased (shares)				501,000	220,000	721,000
Common stock offering			$ 200,000	$ 5,007,000	$ 2,000,000	$ 7,007,000
Class A | Distribution Support Agreement
Subsequent Event [Line Items]
Common stock offering				$ 8,267
Class A | Distribution Support Agreement | NorthStar Realty
Subsequent Event [Line Items]
Common stock purchased (shares)		164,835		682
Common stock offering		$ 1,500,000
Class A | Distribution Support Agreement | RXR Realty
Subsequent Event [Line Items]
Common stock purchased (shares)		54,945		227
Common stock offering		$ 500,000
Subsequent Event | Class A | Distribution Support Agreement | NorthStar Realty
Subsequent Event [Line Items]
Common stock purchased (shares)	645
Common stock offering	$ 5,864
Subsequent Event | Class A | Distribution Support Agreement | RXR Realty
Subsequent Event [Line Items]
Common stock purchased (shares)	215
Common stock offering	$ 1,955