Income Taxes Income Taxes - Reconciliation of the Statutory Federal Tax Rate and the Effective Tax Rate (Details)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax benefit at federal statutory rate	21.00%	21.00%	34.00%
State tax, net of federal benefit	8.00%	15.00%	10.00%
Stock-based compensation	14.00%	31.00%	47.00%
Credits	4.00%	8.00%	8.00%
Foreign rate differential	(2.00%)	(4.00%)	(8.00%)
Change in valuation allowance	(29.00%)	(68.00%)	(46.00%)
Change in federal statutory rate	0.00%	0.00%	(45.00%)
Other	(1.00%)	(3.00%)	(1.00%)
Effective tax rate	15.00%	0.00%	(1.00%)

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 difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to nondeductible expense for share-based payment arrangement.

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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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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 tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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