Income Tax Matters - Reconciliation of Income Tax (Provision) Benefit based on Effective Income Tax Rate and Statutory Tax Rate (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation between income tax provision and statutory income tax provision:
Increase (decrease) in federal valuation allowances	$ 0.0	$ (1.1)	$ (0.2)
State and Local Jurisdiction
Reconciliation between income tax provision and statutory income tax provision:
Increase (decrease) in federal valuation allowances	(1.0)	0.1	1.6
State and tax expense (benefit) before adjustments	1.4	(1.1)	(0.7)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	$ (1.9)	$ 1.5	$ 1.3