Employee Benefit Plans and Other Postretirement Benefits - Change in Benefit Obligations and Change in Fair Value of Plan Assets Related to Pension and Postretirement Plans (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value at beginning of period		$ 267.2
Company contributions		50.0	$ 25.0	$ 25.0
Fair value of plan assets at plan year end		0.0	267.2
Amounts Recognized on Consolidated Balance Sheets:
Noncurrent liabilities		(95.9)	(106.4)
Pension Plans
Change in Benefit Obligations [Roll Forward]
Benefit obligation at beginning of period		1,202.1	1,167.1
Service cost		12.3	14.1	19.3
Interest cost		55.3	55.8	34.7
Plan amendments		2.7	2.9
Actuarial (gain) loss (a)	[1]	(89.8)	23.3
Participant contributions		0.0	0.0
Benefits paid		(63.9)	(61.1)
Benefit obligation at plan year end		1,118.7	1,202.1	1,167.1
Accumulated benefit obligation portion of above		1,098.7	1,173.3
Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value at beginning of period		1,161.6	1,055.3
Actual return on plan assets		9.5	115.9
Company contributions		26.2	51.5
Participant contributions		0.0	0.0
Benefits paid		(63.9)	(61.1)
Fair value of plan assets at plan year end		1,133.4	1,161.6	1,055.3
Overfunded (underfunded) status		14.7	(40.5)
Amounts Recognized on Consolidated Balance Sheets:
Noncurrent assets		63.3	26.5
Current liabilities		(2.7)	(1.7)
Noncurrent liabilities		(45.9)	(65.3)
Accrued asset (obligation) recognized at December 31		14.7	(40.5)
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) (Pre-Tax):
Prior service credit		26.4	29.2
Actuarial gain		81.8	116.0
Total		108.2	145.2
Postretirement Plans
Change in Benefit Obligations [Roll Forward]
Benefit obligation at beginning of period		10.5	9.5
Service cost		0.2	0.2	0.2
Interest cost		0.5	0.5	0.3
Plan amendments		0.0	0.0
Actuarial (gain) loss (a)	[1]	0.2	1.5
Participant contributions		0.4	0.4
Benefits paid		(1.7)	(1.6)
Benefit obligation at plan year end		10.1	10.5	9.5
Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at fair value at beginning of period		0.0	0.0
Actual return on plan assets		0.0	0.0
Company contributions		1.3	1.2
Participant contributions		0.4	0.4
Benefits paid		(1.7)	(1.6)
Fair value of plan assets at plan year end		(0.0)	0.0	$ 0.0
Overfunded (underfunded) status		(10.1)	(10.5)
Amounts Recognized on Consolidated Balance Sheets:
Noncurrent assets		0.0	0.0
Current liabilities		(0.5)	(0.5)
Noncurrent liabilities		(9.6)	(10.0)
Accrued asset (obligation) recognized at December 31		(10.1)	(10.5)
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) (Pre-Tax):
Prior service credit		(3.4)	(3.8)
Actuarial gain		(4.3)	(4.7)
Total		$ (7.7)	$ (8.5)

[1] For the year ended December 31, 2024, the most significant driver of the decrease in the aggregate benefit obligations for the pension and OPEB plans was the actuarial gain due to an increase in the discount rate assumption. Additional gains due to participant experience and the decrease in the salary scale were offset by actuarial losses due to increases in the PCA Hourly Pension Plan benefit multipliers and updated medical assumptions to better reflect anticipated future experience. For the year ended December 31, 2023, the most significant driver of the increase in aggregate benefit obligations for the pension and OPEB plans was the actuarial losses due to a decrease in the discount rate assumption, PCA Hourly Pension Plan benefit multiplier increases, and changes in salary scale and medical claims assumptions to better reflect anticipated future experience.