Agreements and Transactions with Related Parties - Due to Affiliates (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Due to Related Parties [Abstract]
Loan from WPC, including accrued interest	$ 34,569	$ 27,580
Deferred acquisition fees, including accrued interest	9,150	15,305
Shareholder servicing fee liability	6,560	7,422
Accounts payable and other	2,494	2,454
Asset management fees payable	922	866
Current acquisition fees	7	84
Due to affiliate	$ 53,702	$ 53,711