Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and Cash Equivalents	$ 52,728	$ 21,146	$ 9,496
Restricted Cash	18,981	25,336	5,102
Total Cash, Cash Equivalents and Restricted Cash	$ 71,709	$ 46,482	$ 14,598	$ 21,461