Income Taxes - Reconciliation of U.S. Federal Statutory Tax Rate to Effective Tax Rate (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal statutory rate	34.00%	34.00%	34.00%
Stock compensation	25.70%	(1.50%)	(2.50%)
State income tax, net of federal tax benefit	2.30%	(2.30%)	(2.80%)
U.S. research credits	6.70%	18.90%	(0.30%)
Foreign income inclusion in the U.S.	(4.70%)	(10.40%)	(5.00%)
Valuation allowance	149.40%	(47.40%)	(25.80%)
Change in tax reserves	(1.40%)	(0.50%)	(0.50%)
Minority Interest	(1.60%)	(15.90%)	(0.90%)
Tax Reform impact	(344.60%)	(0.00%)	(0.00%)
Intraperiod tax allocation	8.20%	(0.00%)	(0.00%)
ASU 2016-09	126.70%	(0.00%)	(0.00%)
Other, net	0.20%	7.40%	(3.30%)
Effective tax rate	0.90%	(17.70%)	(7.10%)

Effective Income Tax Rate Reconciliation, Intraperiod Tax Allocation, Percent

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Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Percent

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Effective income tax rate reconciliation tax reserve.

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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 attributable to noncontrolling interest income (loss) exempt from income taxes.

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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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