Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating lease cost:
Amortization of right-of-use assets	$ 5.6	$ 4.5	$ 2.7
Interest on lease liabilities	1.3	1.1	0.6
Total operating lease cost	$ 6.9	$ 5.6	$ 3.3