Retirement Benefits

6 Months Ended

Jun. 30, 2021

Retirement Benefits [Abstract]

Retirement Benefits

Retirement Benefits

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

	Three Months Ended				Six Months Ended
	June 30, 2021		June 30, 2020		June 30, 2021		June 30, 2020
	(Dollars in thousands)
Service cost	$	3,789	$	3,489	$	7,577	$	6,975
Interest cost	4,355		5,710		8,709		11,420
Expected return on plan assets	(19,850)		(17,993)		(39,698)		(35,987)
Amortization of prior service cost	58		56		116		111
Amortization of actuarial losses	3,028		2,934		6,054		5,869
Net periodic benefit credit	$	(8,620)	$	(5,804)	$	(17,242)	$	(11,612)

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

	Three Months Ended				Six Months Ended
	June 30, 2021		June 30, 2020		June 30, 2021		June 30, 2020
	(Dollars in thousands)
Service cost	$	28	$	25	$	56	$	48
Interest cost	95		141		190		283
Amortization of prior service credit	(457)		(484)		(913)		(967)
Amortization of actuarial gains	(47)		(69)		(95)		(139)
Net periodic benefit credit	$	(381)	$	(387)	$	(762)	$	(775)