Retirement Plans - Net Periodic Pension Cost of Plan (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 242	$ 224	$ 253
Expected return on assets	(184)	(317)	(295)
Amortization of net loss	97	84	96
Net periodic pension cost	$ 155	$ (9)	$ 54