Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2025

Retirement Benefits [Abstract]

Schedule of Components of Net Periodic Benefit Cost (Credit)

The components of the net periodic pension benefit cost were as follows:

	Three Months Ended				Nine Months Ended
	Sept. 30, 2025		Sept. 30, 2024		Sept. 30, 2025		Sept. 30, 2024
	(Dollars in thousands)
Service cost	$	1,686	$	1,990	$	5,598	$	6,319
Interest cost	8,104		8,592		24,400		25,413
Expected return on plan assets	(10,273)		(10,772)		(30,786)		(32,314)
Amortization of prior service cost	46		22		59		68
Amortization of actuarial losses	1,726		2,232		5,502		5,937
Net periodic benefit cost	$	1,289	$	2,064	$	4,773	$	5,423

The components of the net periodic other postretirement benefit (credit) cost were as follows:

	Three Months Ended				Nine Months Ended
	Sept. 30, 2025		Sept. 30, 2024		Sept. 30, 2025		Sept. 30, 2024
	(Dollars in thousands)
Service cost	$	—	$	8	$	10	$	22
Interest cost	20		151		322		483
Amortization of prior service credit	(16)		(5)		(45)		(15)
Amortization of actuarial gains	(414)		(102)		(586)		(270)
Net periodic benefit (credit) cost	$	(410)	$	52	$	(299)	$	220