Postretirement Health Care and Life Insurance Benefits - Reconciliation of Postretirement Plans' Funded Status to the Balance Sheet (Details) - Postretirement Health Care and Life Insurance Benefits - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Change in benefit obligation
Accumulated postretirement benefit obligation at beginning of period	$ 145.4	$ 178.0
Service cost	0.3	0.5	$ 0.5
Interest cost	7.8	9.1	10.2
Plan amendments	0.0	(6.5)
Benefits paid and administrative fees	(15.2)	(18.8)
Actuarial gain	(8.1)	(16.9)
Accumulated postretirement benefit obligation at end of period	130.2	145.4	178.0
Change in plan assets
Fair value of plan assets at beginning of period	9.1	11.3	$ 14.3
Actual return on plan assets	0.8	0.5
Employer contributions	12.2	15.3
Benefits paid and administrative fees (net of Medicare Part D reimbursements)	(15.2)	(18.8)
Fair value of plan assets at end of period	11.3	14.3
Funded status at end of period	(121.1)	(134.1)
Less: Current portion (included in “Accounts payable and accrued expenses”)	11.9	13.7
Noncurrent obligation (included in “Accrued postretirement benefit costs”)	$ 109.2	$ 120.4

Postretirement Health Care and Life Insurance Benefits - Reconciliation of Postretirement Plans' Funded Status to the Balance Sheet (Details) - Postretirement Health Care and Life Insurance Benefits - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2025

Dec. 31, 2024

Dec. 31, 2023

Change in benefit obligation

Accumulated postretirement benefit obligation at beginning of period

$ 145.4

$ 178.0

Service cost

0.3

0.5

$ 0.5

Interest cost

7.8

9.1

10.2

Plan amendments

0.0

(6.5)

Benefits paid and administrative fees

(15.2)

(18.8)

Actuarial gain

(8.1)

(16.9)

Accumulated postretirement benefit obligation at end of period

130.2

145.4

178.0

Change in plan assets

Fair value of plan assets at beginning of period

9.1

11.3

$ 14.3

Actual return on plan assets

0.8

0.5

Employer contributions

12.2

15.3

Benefits paid and administrative fees (net of Medicare Part D reimbursements)

(15.2)

(18.8)

Fair value of plan assets at end of period

11.3

14.3

Funded status at end of period

(121.1)

(134.1)

Less: Current portion (included in “Accounts payable and accrued expenses”)

11.9

13.7

Noncurrent obligation (included in “Accrued postretirement benefit costs”)

$ 109.2

$ 120.4

- Definition

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.