v3.20.4

Income Taxes - Additional Information (Details) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 USD ($) Ownership | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Income Taxes Disclosure [Line Items] |  |  |
Increased in valuation allowance | $ 169,700 | $ 178,900 |
Research and development tax credit carryforwards | 104,110 | 73,442 |
Unrecognized tax benefits | 29,175 | $ 19,487 | $ 14,541
Accrued interest and penalties | $ 200 |  |
Income tax examination description | The Company is currently under examination by Texas Comptroller for calendar tax years 2015, 2016, and 2017. All tax years remain subject to examination by federal and state authorities. These audits include questioning the timing and amount of deductions; the nexus of income among various tax jurisdictions; and compliance with federal, state, and local tax laws. |  |
Research and Development Credits |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Unrecognized tax benefits | $ 28,300 |  |
Federal |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 1,423,100 |  |
Net operating loss carryforwards, expiration beginning year | 2028 |  |
Research and development tax credit carryforwards | $ 82,600 |  |
Tax credit carryforwards, expiration beginning year | 2028 |  |
State |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 1,273,900 |  |
Net operating loss carryforwards, expiration year | 2020 |  |
Research and development tax credit carryforwards | $ 59,400 |  |
Tax credit carryforwards, expiration beginning year | 2035 |  |
UK |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 17,600 |  |
Research and development tax credit carryforwards | 300 |  |
Denmark |  |  |
Income Taxes Disclosure [Line Items] |  |  |
Net operating loss carryforwards | $ 800 |  |
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 | $ 900 |  |

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