Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018
Increase (decrease) in deferred tax asset valuation allowance	$ (11.7)	$ (7.7)
Operating Loss Carryforwards						$ 568.0
Operating Loss Carryforwards, No Expiration	131.4		$ 131.4
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount			31.7	$ 0.6	$ 71.3
Provision (benefit) for income taxes			(0.1)	(15.6)	39.1
Liability for Uncertain Tax Positions, Noncurrent	2.9		2.9	1.9	$ 1.0
Income Tax Examination, Penalties and Interest Expense Reduction			(0.2)	(0.1)
Unrecognized Tax Benefits, Income Tax Penalties Expense Reduction			(1.0)	(0.9)
Income Tax Examination, Penalties and Interest Accrued	0.3		$ 0.3	$ 0.1
Federal Statutory Income Tax Rate, Percent			21.00%	21.00%	21.00%
Deferred Tax Assets, Valuation Allowance	382.4		$ 382.4	$ 414.1
Domestic Tax Authority [Member]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount			$ 19.4
State and Local Jurisdiction [Member]
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent			15.00%	2.00%	1.00%
Operating Loss Carryforwards, Valuation Allowance	$ 488.4		$ 488.4
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount			$ 12.3	$ 12.1	$ 40.7