Income Taxes - NOL Carryforwards and Federal Research and Development Tax Credits (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Domestic Tax Authority
Operating Loss and Tax Credit Carryforwards [Line Items]
Net operating losses, amount	$ 224,476
Net operating losses, not subject to expiration, amount	64,371
Tax credits, amount	9,031
State
Operating Loss and Tax Credit Carryforwards [Line Items]
Net operating losses, amount	124,881
Tax credits, amount	10,436
Foreign Tax Authority
Operating Loss and Tax Credit Carryforwards [Line Items]
Net operating losses, amount	$ 536