Retirement Plans - Net Periodic Pension Cost (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 38	$ 48
Expected return on assets	(48)	(51)
Amortization of net loss	21	20
Net periodic pension cost	$ 11	$ 17