Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2020

Retirement Benefits, Description [Abstract]

Schedule of Net Benefit Costs

For the three months ended March 31, 2020 and 2019, the components of net periodic benefit cost are as follows:

	Three months ended March 31
(Dollars in thousands)	2020			2019
Service cost	$	3,457		$	3,113
Interest cost	8,531			9,291
Expected return on assets	(16,409		)	(15,635		)
Amortization of prior service cost	—			14
Amortization of net actuarial loss	6,264			2,741
Net periodic cost (benefit)	$	1,843		$	(476	)