Summary of Significant Accounting Policies - Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Summary of Significant Accounting Policies
Unrecognized tax benefits			$ 0.0	$ 0.0
Deferred tax asset		$ 12.1
Increase in deferred income tax expense		$ 12.1
Effective Income Tax Rate	21.00%	35.00%

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of income tax expense for remeasurement of deferred tax asset from change in tax rate pursuant to Tax Cuts and Jobs Act.

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Amount of income tax expense (benefit) for measurement period adjustment from accounting for tax effect pursuant to Tax Cuts and Jobs Act.

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Amount of unrecognized tax benefits.

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