Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2020

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost

The components of the net periodic pension benefit credit for the three months ended March 31 were as follows:

	2020		2019
	(Dollars in thousands)
Service cost	$	3,486	$	3,258
Interest cost	5,710		7,049
Expected return on plan assets	(17,993)		(15,113)
Amortization of prior service cost	55		19
Amortization of actuarial losses	2,934		4,119
Net periodic benefit credit	$	(5,808)	$	(668)

The components of the net periodic other postretirement benefit credit for the three months ended March 31 were as follows:

	2020		2019
	(Dollars in thousands)
Service cost	$	23	$	22
Interest cost	142		185
Amortization of prior service credit	(483)		(582)
Amortization of actuarial gains	(70)		(167)
Net periodic benefit credit	$	(388)	$	(542)