Retirement Benefits (Tables)

6 Months Ended

Jun. 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				Six Months Ended
	June 30, 2022		June 30, 2021		June 30, 2022		June 30, 2021
	(Dollars in thousands)
Service cost	$	3,270	$	3,789	$	6,570	$	7,577
Interest cost	5,140		4,355		10,299		8,709
Expected return on plan assets	(17,315)		(19,850)		(34,629)		(39,698)
Amortization of prior service cost	53		58		108		116
Amortization of actuarial losses	1,157		3,028		2,312		6,054
Net periodic benefit credit	$	(7,695)	$	(8,620)	$	(15,340)	$	(17,242)

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

	Three Months Ended				Six Months Ended
	June 30, 2022		June 30, 2021		June 30, 2022		June 30, 2021
	(Dollars in thousands)
Service cost	$	26	$	28	$	51	$	56
Interest cost	109		95		218		190
Amortization of prior service credit	(416)		(457)		(832)		(913)
Amortization of actuarial gains	(77)		(47)		(154)		(95)
Net periodic benefit credit	$	(358)	$	(381)	$	(717)	$	(762)