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Income Taxes - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Income Tax Disclosure [Abstract] |  |
Increase in valuation allowance | $ 352,700 |
Operating Loss Carryforwards [Line Items] |  |
Increase in valuation allowance | 352,700 |
Deferred tax assets | 874,145 | $ 507,268
Federal |  |
Operating Loss Carryforwards [Line Items] |  |
Net operating losses | 2,260,000 |
Net operating losses that begin to expire in 2030 | 380,100 |
Net operating losses that will carry-forward indefinitely | 1,880,000 |
Federal | Research and development |  |
Operating Loss Carryforwards [Line Items] |  |
Tax credit carry-forwards | 73,300 |
State |  |
Operating Loss Carryforwards [Line Items] |  |
Net operating losses | 1,700,000 |
Net operating losses that begin to expire in 2030 | 1,700,000 |
State | Research and development |  |
Operating Loss Carryforwards [Line Items] |  |
Tax credit carry-forwards | 26,100 |
State | Federal Orphan Drug |  |
Operating Loss Carryforwards [Line Items] |  |
Tax credit carry-forwards | 2,000 |
State | Investment tax credit |  |
Operating Loss Carryforwards [Line Items] |  |
Tax credit carry-forwards | $ 3,900 |

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