v3.19.3.a.u2

Income Taxes - Additional Information (Details) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 USD ($) Ownership | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Income Taxes Disclosure [Line Items] |  |  |
Increased in valuation allowance | $ 178,900 | $ 114,100 |
Research and development tax credit carryforwards | 73,442 | 39,344 |
Unrecognized tax benefits | 19,487 | $ 14,541 | $ 5,843
Accrued interest and penalties | 300 |  |
Research and Development Credits |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Unrecognized tax benefits | 18,300 |  |
Federal |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 1,005,400 |  |
Net operating loss carryforwards, expiration beginning year | 2028 |  |
Research and development tax credit carryforwards | $ 58,300 |  |
Tax credit carryforwards, expiration beginning year | 2028 |  |
State |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 851,700 |  |
Net operating loss carryforwards, expiration year | 2019 |  |
Research and development tax credit carryforwards | $ 40,000 |  |
Tax credit carryforwards, expiration beginning year | 2035 |  |
UK |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 9,400 |  |
Research and development tax credit carryforwards | 200 |  |
Denmark |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 100 |  |
Section 382 |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Number of ownership changes for income tax purposes | Ownership | 4 |  |
International |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Unrecognized tax benefits | $ 1,200 |  |

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