Income Tax - Effective Income Tax Reconciliation (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. Federal statutory rate	34.00%	34.00%	34.00%
State rate, net of federal benefit	2.80%	7.80%	1.30%
Permanent differences:
Change in tax rate	16.40%	(113.00%)	0.00%
Impact of tax reform	(16.40%)	(0.00%)	(0.00%)
Deferred tax adjustment	(0.30%)	(19.10%)	0.00%
Stock based compensation	0.10%	28.90%	(1.10%)
Foreign tax rate difference	0.30%	19.30%	(0.40%)
Fair value measurement of warrants	(4.50%)	0.00%	0.00%
Other	(1.60%)	3.00%	0.00%
Change in valuation allowance	(67.90%)	40.00%	(33.90%)
Income tax provision (benefit)	(37.10%)	0.90%	(0.10%)

Effective Income Tax Rate Reconciliation, Deferred Tax Adjustment

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Effective Income Tax Rate Reconciliation, Fair Value Measurement of Warrants

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Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent

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

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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