Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 1,478	$ 5,409
Restricted cash	104,904	49,098
Total cash, cash equivalents and restricted cash	$ 106,382	$ 54,507	$ 2,174	$ 4,102