Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Valuation allowance	$ 10.7	$ 8.3
Excess tax benefit from tax cuts and jobs act	67.5	(19.4)	$ (19.6)
Income tax refund receivable related to CARES Act	15.4
Income taxes	2.4	15.3	$ 15.3
Current tax benefit for transition tax	1.5
State
Income Taxes
Operating loss carryforwards, amount	$ 20.5
State | Minimum
Income Taxes
Operating loss carryforwards, expiration year	2021
State | Maximum
Income Taxes
Operating loss carryforwards, expiration year	2040
Accounting Standards Update 2016-09
Income Taxes
Excess tax benefit from tax cuts and jobs act	$ 0.1	$ 0.5