Income Taxes - Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S. Statutory Rate	34.00%	34.00%	34.00%
Change in valuation allowance	(11.80%)	9.90%	8.90%
State taxes (net of federal benefit)	(4.40%)	3.80%	(33.60%)
Federal research and development credit	67.40%	(60.80%)	(136.00%)
Incentive stock options	(46.20%)	19.50%	83.60%
Unrecognized tax benefits	(47.10%)	28.80%	34.00%
Preferred stock warrant revaluation	12.60%	(22.40%)	34.40%
Other, net	(15.50%)	2.90%	(1.00%)
Effective income tax rate	(11.00%)	15.70%	24.30%

Effective income tax rate reconciliation change in preferred stock warrant revaluation.

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

+ References

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-Publisher FASB
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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 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 income tax contingencies. Includes, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

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