Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2020

Retirement Benefits, Description [Abstract]

Schedule of Net Benefit Costs

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

	Three months ended June 30				Six months ended June 30
(Dollars in thousands)	2020		2019		2020		2019
Service cost	$	3,682	$	3,271	$	7,139	$	6,384
Interest cost	8,568		9,338		17,099		18,629
Expected return on assets	(16,435)		(15,661)		(32,844)		(31,296)
Amortization of prior service cost	—		14		—		28
Amortization of net actuarial loss	6,398		2,721		12,662		5,462
Net periodic cost (benefit)	$	2,213	$	(317)	$	4,056	$	(793)