Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2017 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Summary Of Net Deferred Tax Assets [Line Items] | ||||
| Income Tax Expense (Benefit) | $ 1.6 | $ 0.7 | $ 0.1 | |
| Share-based compensation, excess tax benefits | $ 161.8 | |||
| Net operating loss carryforwards | 188.7 | 101.9 | ||
| Capitalized research and development expenses | 8.4 | 14.3 | ||
| Tax credits | 47.8 | 30.7 | ||
| Share-based compensation | 13.8 | 24.9 | ||
| Fixed and intangible assets | 0.4 | 0.0 | ||
| Accrued liabilities and reserves | 20.9 | 26.0 | ||
| Total gross deferred tax assets | 280.0 | 197.8 | ||
| Less: valuation allowance | (263.5) | (193.4) | ||
| Fixed assets and acquired intangibles assets | (0.1) | (4.3) | ||
| Convertible debt discount | (15.9) | 0.0 | ||
| Unrealized exchange gain | 0.4 | 0.0 | ||
| Net deferred tax asset (liability) | $ 0.1 | 0.1 | ||
| Accounting Standards Update 2016-09 [Member] | ||||
| Summary Of Net Deferred Tax Assets [Line Items] | ||||
| Deferred Income Tax Assets, Net | $ 161.8 | |||
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- Definition Deferred Tax Liabilities, Convertible Debt Discount No definition available.
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- Definition Excess tax benefits from share-based compensation No definition available.
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- Definition Summary Of Net Deferred Tax Assets [Line Items] No definition available.
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- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets including goodwill. No definition available.
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences from provisions, reserves, allowances, and accruals, classified as other. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued liabilities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from intangible assets including goodwill. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from intangible assets other than goodwill. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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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- Details
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