Retirement Plans - Net Periodic Pension Cost - Pension Plan (Details) - Pension plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cost components:
Service cost	$ 0	$ 0	$ (15)
Interest cost	(389)	(365)	(386)
Expected return on plan assets	522	585	531
Net amortization and deferral	(75)	(64)	(122)
Settlement recognition	0	0	47
Total net periodic pension earnings/(cost)	$ 58	$ 156	$ 55