Retirement Plans and Other Postretirement Benefits (Tables)

3 Months Ended

Mar. 31, 2020

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost (Income)

Components of net periodic benefit cost were as follows: 

	Three Months Ended March 31,
	2020		2019		2020		2019
(Dollars in thousands)	Retirement Plans				Other Post Retirement Benefits
Service cost	$	117	$	109	$	28	$	17
Interest cost	417		476		24		23
Expected return on plan assets	(816)		(771)		—		—
Amortization of net actuarial loss	291		294		6		—
Accretion of prior service cost	—		(45)		—		—
Net periodic benefit cost	$	9	$	63	$	58	$	40