Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2020

Retirement Benefits, Description [Abstract]

Schedule of Net Benefit Costs

For the three and nine months ended September 30, 2020 and 2019, the components of net periodic benefit cost are as follows:

	Three months ended September 30				Nine months ended September 30
(Dollars in thousands)	2020		2019		2020		2019
Service cost	$	3,570	$	3,191	$	10,709	$	9,575
Interest cost	8,549		9,316		25,648		27,945
Expected return on assets	(16,423)		(15,647)		(49,267)		(46,943)
Amortization of prior service cost	—		15		—		43
Amortization of net actuarial loss	6,332		2,730		18,994		8,192
Net periodic cost (benefit)	$	2,028	$	(395)	$	6,084	$	(1,188)