Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Balance of total restricted cash	$ 6,020
Cash and cash equivalents	7,135	$ 12,039	$ 5,667
Restricted cash included in current assets	6,020	6,020	1,520
Restricted cash included in long-term assets	0		5,000
Total cash, cash equivalents, and restricted cash shown in the Consolidated Statements of Cash Flows	$ 13,155	$ 18,059	$ 12,187	$ 14,386