Income Taxes - Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2020 USD ($)
Tax Credit Carryforward [Line Items]
Taxable income required for full realization of deferred tax assets	$ 882.4
Federal | Research and development tax credit carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward	21.4
Federal | Tax credit that can be carried forward indefinitely
Tax Credit Carryforward [Line Items]
Tax credit carryforward	407.3
State | Research and development tax credit carryforward
Tax Credit Carryforward [Line Items]
Tax credit carryforward	$ 16.9