Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 2,033	$ 5,409
Restricted cash	9,151	49,098
Total cash, cash equivalents and restricted cash	$ 11,184	$ 54,507	$ 9,026	$ 4,102