Description of Business and Summary of Significant Accounting Policies - Adjustments For New Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in operating activities	$ 5,355	$ (9,352)	$ (22,221)
Net cash provided by (used in) financing activities	149,822	1,744	3,545
Net cash, cash equivalents, restricted cash and restricted cash equivalents	$ 144,813	(21,175)	(23,243)
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in operating activities		(9,345)	(22,160)
Net cash provided by (used in) financing activities		1,345	1,723
Net cash, cash equivalents, restricted cash and restricted cash equivalents		(21,567)	(25,004)
Restatement Adjustment | Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in operating activities		(7)	(61)
Net cash provided by (used in) financing activities		399	1,822
Net cash, cash equivalents, restricted cash and restricted cash equivalents		$ (392)	$ (1,761)