Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and Cash Equivalents	$ 61,834	$ 21,146	$ 11,607
Restricted Cash	15,679	25,336	5,619
Total Cash, Cash Equivalents and Restricted Cash	$ 77,513	$ 46,482	$ 17,226	$ 21,461