Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2022

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost

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

	Three Months Ended				Nine Months Ended
	Sept. 30, 2022		Sept. 30, 2021		Sept. 30, 2022		Sept. 30, 2021
	(Dollars in thousands)
Service cost	$	2,937	$	3,177	$	9,507	$	10,754
Interest cost	5,131		4,579		15,430		13,288
Expected return on plan assets	(17,220)		(19,892)		(51,849)		(59,590)
Amortization of prior service cost	62		67		170		183
Amortization of actuarial losses	1,370		3,464		3,682		9,518
Net periodic benefit credit	$	(7,720)	$	(8,605)	$	(23,060)	$	(25,847)

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

	Three Months Ended				Nine Months Ended
	Sept. 30, 2022		Sept. 30, 2021		Sept. 30, 2022		Sept. 30, 2021
	(Dollars in thousands)
Service cost	$	5	$	25	$	56	$	81
Interest cost	96		82		314		272
Amortization of prior service credit	(415)		(460)		(1,247)		(1,373)
Amortization of actuarial gains	(75)		(137)		(229)		(232)
Net periodic benefit credit	$	(389)	$	(490)	$	(1,106)	$	(1,252)