Income Taxes - Components of Income Tax (Benefit) Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Expected Statutory expense (benefit)	$ (7,627)	$ (5,195)	$ (3,977)
U.S. TCJA recovery of alternative minimum tax credits	0	(73)	0
Change in the fair values of derivative and amortization of debt discount	0	2,939	2,584
Other non-deductible expenses	256	24	63
Change in valuation allowance including U.S. TCJA rate reduction	6,572	(2,012)	590
Reduction in deferred tax assets related to U.S. TCJA rate reduction	0	7,504	0
Change to Accounting for Equity Compensation Windfalls	0	(1,112)	0
Tax rate differential - foreign vs. U.S.	791	(2,276)	822
State income taxes, net of federal benefit	23	13	23
Shortfalls related to stock compensation expense	0	129	154
Prior year true-up	(93)	(13)	0
Exchange gain	16	(13)	28
Total income tax (benefit) expense	$ (62)	$ (85)	$ 287