Debt and Credit Arrangements - Notes Interest Accretion Schedule (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Nov. 06, 2017
Debt Instrument
Interest accretion of convertible notes discount	$ 0.0	$ 0.0	$ 8.0
Interest expense excluding amortization	28.8	10.7	17.7
Total interest expense	25.7	11.7	18.1
Financing costs amortization	2.9	8.3	4.3
Convertible Debt | Convertible Notes, due 2024
Debt Instrument
Interest accretion of convertible notes discount	0.0	0.0	8.0
Interest expense excluding amortization	4.0	2.6	2.6
Total interest expense	4.0	2.6	10.6
Financing costs amortization	$ 0.9	$ 0.9	$ 0.7
Debt instrument stated interest rate (percent)	1.50%	1.00%	1.00%	1.00%