Income Tax Matters - Reconciliation of Income Tax (Provision) Benefit based on Effective Income Tax Rate and Statutory Tax Rate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reconciliation between income tax provision and statutory income tax provision:
Amount of federal income tax (provision) benefit based on the statutory rate	$ (13.3)	$ (11.8)	$ 8.0
Decrease in federal valuation allowances	0.0	0.0	1.1
Non-deductible compensation expense	(2.2)	(1.6)	(0.9)
Non-deductible (expense) benefit	(0.2)	0.2	(1.0)
State income tax (provision) benefit, net of federal benefit	(1.4)	1.5	(0.5)
Research and development credit	1.2	3.2	2.2
Foreign income tax expense	(0.4)	(0.3)	(0.3)
Foreign undistributed earnings	(0.4)	(0.3)	(0.3)
Income tax (provision) benefit	$ (16.7)	$ (9.1)	$ 8.3