Income Tax Matters - Income (Loss) Before Income Taxes by Geographic Area (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Domestic	$ 48.0	$ (44.6)	$ (30.2)
Foreign	8.3	6.7	6.2
Income (loss) before income taxes	$ 56.3	$ (37.9)	$ (24.0)