Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 652.2		$ 631.2		$ 692.5
Other comprehensive (loss) income, net of tax		7.4		9.9		6.9
Ending balance		668.0		652.2		631.2
Defined Benefit Plans:
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		11.0		2.8		(21.4)
Less: income tax benefit (expense)	[1]	(0.1)		(1.0)		(1.2)
Net (gain) loss reclassified from AOCI to Net income (loss)		0.4		3.2		3.7
Other comprehensive (loss) income, net of tax		8.1		8.2		24.2
Ending balance		19.1		11.0		2.8
Defined Benefit Plans: Net Actuarial Gain
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Unrealized loss on cash flow hedges		12.2		4.3		27.0
Less: income tax benefit (expense)		(2.8)		(1.0)		(6.5)
Net unrealized gain (loss) on available for sale securities, cash flow hedges and fair value hedges		9.4		3.3		20.5
Reclassification from AOCI	[2],[3]	(2.0)		(1.1)
Defined Benefit Plans: Net Prior Service (Cost) Credit
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Unrealized loss on cash flow hedges		(2.2)		2.2
Less: income tax benefit (expense)		0.5		(0.5)
Net unrealized gain (loss) on available for sale securities, cash flow hedges and fair value hedges		(1.7)		1.7
Reclassification from AOCI	[3]	2.5		5.3		4.9
Cash Flow Hedges:
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		2.1	[4]	0.4	[4]	17.7
Unrealized loss on cash flow hedges		(0.2)		(10.7)		(12.2)
Less: income tax benefit (expense)				2.5		2.9
Net unrealized gain (loss) on available for sale securities, cash flow hedges and fair value hedges		(0.2)		(8.2)		(9.3)
Reclassification from AOCI		(0.9)		12.9		(10.5)
Reclassification due to forecasted transactions probable of not occurring		0.2
Less: income tax benefit (expense)	[1]	0.2		(3.0)		2.5
Net (gain) loss reclassified from AOCI to Net income (loss)		(0.5)		9.9		(8.0)
Other comprehensive (loss) income, net of tax		(0.7)		1.7		(17.3)
Ending balance	[4]	1.4		2.1		0.4
Accumulated Other Comprehensive (Loss) Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		13.1		3.2		(3.7)
Other comprehensive (loss) income, net of tax		7.4		9.9		6.9
Ending balance		$ 20.5		$ 13.1		$ 3.2

[1] Income tax amounts reclassified out of AOCI were included as a component of Income tax (provision) benefit.

[2] Amounts amortized out of AOCI during the year ended December 31, 2024 include net actuarial gains recognized on a pro-rata basis in conjunction with a group annuity purchase (see Note 5).

[3] Amounts amortized out of AOCI related to pension and other postretirement and postemployment benefits were included within Net periodic postretirement and postemployment benefit cost (see Note 5).

[4] As of December 31, 2024, we estimate a net mark-to-market gain before tax of $1.9 million in AOCI will be reclassified into Net income (loss) upon settlement within the next 12 months.