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Income Taxes - Reconciliation of Reported Estimated Income Tax Benefit (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Income Taxes [Abstract] |  |  |
United States federal tax at statutory rate | $ (7,049) | $ (13,410) | $ (91)
State taxes (net of federal benefit) | (897) | (1,608) | 609
Deferred income tax adjustments | 661 | 0 | (855)
Deferred state blended rate adjustments | (493) | 3,034 | (344)
Research credit, net | (3,296) | (2,228) | (226)
Transaction cost deduction | 0 | (379) | 0
Transaction cost deduction - prior year adjustment | 0 | (564) | 0
Orphan drug credit, net | (106) | (139) | (843)
Other permanent items | (25) | (382) | 3
Equity-based compensation | 1,102 | 756 | 241
Fair value adjustment of preferred stock warrant liability | 0 | 0 | 219
Change in valuation allowance | 10,103 | 14,920 | 1,287
Income tax expense/(benefit) | $ 0 | $ 0 | $ 0

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- Definition Amount 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 deferred tax adjustments. + References No definition available. + Details
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- Definition Amount 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 deductions. Including, but not limited to, extraterritorial income exclusion deduction, qualified production activity deduction, dividend deduction, deduction for dividend paid to employee stock ownership plan, Medicare prescription drug benefit subsidy deduction, and other deductions related to prior year adjustment. + References No definition available. + Details
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Income Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6515339 + Details
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