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Income Taxes - Narrative (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Operating Loss Carryforwards [Line Items] |  |
TCJA, Provisional tax expense (benefit) offset by valuation allowance | $ 105,700,000 | $ 105,700,000
Change in tax rate reducing deferred tax asset | 105,300,000 |
TCJA, Provisional income tax expense (benefit) |  | 0
Foreign earnings repatriated | 0 | 0
Cumulative foreign deficits | 24,600,000 | 41,200,000
Increase in opening balance of deferred tax assets | 400,000 |
Increase in valuation allowance | 66,600,000 |
Deferred Tax Assets, Tax Benefits Credited to Additional Paid In Capital | $ 56,200,000 |
Tax credit carryforward, expiration date | Jan. 01, 2020 |
Tax credit carryforwards subject to expiration | $ 2,100,000 |
Valuation allowance amount | (330,100,000) | (263,500,000)
Unrecognized tax benefits | 0 |
Federal |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | $ 578,700,000 |
Operating loss carryforwards, expiration dates | Jan. 01, 2027 |
Federal and state research and development tax credit carryforwards | $ 41,100,000 |
Deferred Tax Assets, Tax Credit Carryforwards, Research, Subject to Expiration | 30,000 |
State and Local Jurisdiction |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | $ 417,200,000 |
Operating loss carryforwards, expiration dates | Jan. 01, 2025 |
Federal and state research and development tax credit carryforwards | $ 41,400,000 |
Foreign Tax Authority |  |
Operating Loss Carryforwards [Line Items] |  |
Operating loss carryforwards | 129,300,000 |
Accounting Standards Update 2016-09 |  |
Operating Loss Carryforwards [Line Items] |  |
Deferred income tax assets |  | $ 161,800,000
Measurement period adjustment |  |
Operating Loss Carryforwards [Line Items] |  |
Increase in valuation allowance | 400,000 |
Continuing Operations |  |
Operating Loss Carryforwards [Line Items] |  |
Increase in valuation allowance | 56,900,000 |
Additional paid-in capital |  |
Operating Loss Carryforwards [Line Items] |  |
Increase in valuation allowance | 11,900,000 |
Goodwill |  |
Operating Loss Carryforwards [Line Items] |  |
Increase in valuation allowance | $ 2,200,000 |

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