Pension and Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2022

Retirement Benefits [Abstract]

Schedule of Components of Net Periodic Benefit Cost (Credit)

The estimated components of the recorded net periodic benefit cost (credit) for pension and postretirement benefits are as follows:

	Pension						Postretirement Benefits
	Three Months Ended September 30,
	2022			2021			2022			2021
	(Dollars in Millions)
Service cost	$	12.0		$	11.6		$	—		$	—
Interest cost		10.3			8.9			0.1			0.1
Expected return on assets		(19.3	)		(17.7	)		—			—
Amortization of:
Prior service cost (credit)		1.3			0.2			(0.2	)		(0.2	)
Actuarial loss (gain)		1.0			3.0			(0.1	)		—
Settlement charge		4.5			—			—			—
Net periodic benefit cost (credit)	$	9.8		$	6.0		$	(0.2	)	$	(0.1	)

	Pension						Postretirement Benefits
	Nine Months Ended September 30,
	2022			2021			2022			2021
	(Dollars in Millions)
Service cost	$	36.1		$	34.7		$	—		$	—
Interest cost		30.9			26.7			0.2			0.2
Expected return on assets		(58.0	)		(52.8	)		—			—
Amortization of:
Prior service cost (credit)		3.7			0.5			(0.5	)		(0.5	)
Actuarial loss (gain)		3.0			9.2			(0.2	)		(0.1	)
Settlement charge		4.5			—			—			—
Net periodic benefit cost (credit)	$	20.2		$	18.3		$	(0.5	)	$	(0.4	)