Income Taxes - Reconciliation Between Effective Tax Rate and Statutory Rate (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
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Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Reconciliation Of Statutory Federal Tax Rate [Line Items] | |||
| Income taxes at statutory rates | $ (17.0) | $ (22.7) | $ (20.1) |
| State income tax, net of federal benefit | (0.7) | 1.2 | (1.0) |
| Permanent items | 0.7 | 0.8 | 0.3 |
| Research and development credits | (13.3) | (11.7) | (10.0) |
| Foreign rate differential | 5.4 | 4.5 | 0.0 |
| Stock and officers compensation | (10.4) | 4.0 | 3.1 |
| Rate change | (0.1) | (0.1) | 0.2 |
| Unrecognized tax benefits | (15.4) | 27.7 | 0.0 |
| Impact of Tax Cuts and Jobs Act of 2017 | 105.7 | 0.0 | 0.0 |
| Other | (2.2) | 0.0 | 0.2 |
| Change in valuation allowance | (51.1) | (3.0) | 27.4 |
| Income taxes at effective rates | $ 1.6 | $ 0.7 | $ 0.1 |
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- Definition Effective Income Tax Reconciliation, Impact of TCJA No definition available.
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- Definition Effective Income Tax Reconciliation, Permanent Items No definition available.
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- Definition Reconciliation Of Statutory Federal Tax Rate [Line Items] No definition available.
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 increase (decrease) in the valuation allowance for deferred tax assets. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 increase (decrease) in the income tax rates. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 foreign income tax expense (benefit). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 nondeductible equity-based compensation costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 other adjustments. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 state and local income tax expense (benefit). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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 research tax credit. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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