Retirement Plans - Net Periodic Pension Cost (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 38	$ 48	$ 76	$ 96
Expected return on assets	(48)	(51)	(96)	(102)
Amortization of net loss	21	20	42	40
Net periodic pension cost	$ 11	$ 17	$ 22	$ 34