Employee Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2024

Retirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures

The following summarizes the components of net periodic benefit for our qualified and supplemental pension plans:

(Dollars in millions)	Three months ended June 30,				Six months ended June 30,
	2024		2023		2024		2023
Service cost	$	2	$	2	$	3	$	3
Non-service (benefit) costs:
Interest cost	3		3		6		6
Expected return on plan assets	(6)		(5)		(11)		(10)
Amortization of actuarial loss (gain) and prior   service cost	1		(1)		1		(2)
Other	—		—		—		(5)
Total non-service benefit	(2)		(3)		(4)		(11)
Net periodic benefit	$	—	$	(1)	$	(1)	$	(8)