Income Taxes - Components of Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Effective income tax rate reconciliation, percent
U.S. federal statutory rate	34.00%	34.00%
Effective income tax rate reconciliation, amount
Expected tax benefit	$ (1,766)	$ (8,307)
Net tax effects of:
Foreign tax rate differential	(77)	1,331
State taxes, net of federal benefit	(362)	219
Return to provision adjustment	(48)	13,386
Research and other credits	2,719	443
Permanent difference on convertible notes and warrants	(169)	2,923
Goodwill impairment	0	533
Other	86	61
Change in deferred tax asset valuation allowance	(298)	(11,547)
Total	$ 85	$ (958)