Income Taxes - Reconciliation of Income Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of the income tax provision computed at statutory tax rates to the income tax provision
Statutory federal income taxes	$ 17.3	$ 29.2	$ 24.5
State income taxes	0.6	4.8	0.8
Tax status change & other true-ups	0.1	0.8	0.9
Other true-ups	0.3	(2.5)	0.8
Equity compensation	3.8	(1.0)	(0.3)
Other permanent differences	(2.4)	(0.4)	(0.4)
Research and development tax credits	2.5	2.2
Uncertain tax positions	(0.1)	(0.2)	3.7
Change in valuation allowance	(8.3)	(2.3)	3.9
Income tax (expense) benefit, net	$ 13.8	$ 30.6	$ 33.9