Income Taxes - Components of the income tax expense (benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Current expense (benefit)
Federal	$ 0.7
State	(0.7)	$ 0.2	$ 0.4
Foreign	1.2	1.5	2.5
Total	1.2	1.7	2.9
Deferred expense (benefit)
State	(0.4)	(0.1)	0.5
Total	(0.4)	(0.1)	0.5
Total income tax expense (benefit)	$ 0.8	$ 1.6	$ 3.4