Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Taxes at federal statutory rate		$ (13,420)	$ (6,650)	$ (6,028)
State taxes, net of federal benefit		(236)	(208)	(236)
Effect of tax rate differential for foreign subsidiary		(1,646)	(2,985)	(2,641)
Valuation allowance, including tax benefits of stock activity		(16,962)	10,272	3,894
Tax rate change		34,732	0	0
Foreign taxes on unremitted earnings	$ 1,200	0	1,204	2,085
Stock-based compensation		224	441	134
Foreign withholding taxes		295	260	180
Return to provision adjustments		(2,931)	1,062	1,131
Subpart F income inclusion		2,998	906	5,914
SEC settlement penalty		959	0	0
Business combination		(1,914)	0	0
Other		1,558	(157)	170
Tax provision		$ 3,657	$ 4,145	$ 4,603

Effective Income Tax Rate Reconciliation, Acquisition of Business, Amount

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Effective Income Tax Rate Reconciliation, Penalty Settlement, Amount

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Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Including Stock Activity

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Income Tax Reconciliation, Return to Provision Adjustments

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Income Tax Reconciliation, Subpart F Income Inclusion

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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