Retirement Plans - Net Periodic Pension Cost (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 48	$ 60	$ 96	$ 120
Expected return on assets	(51)	(46)	(102)	(92)
Amortization of net loss	20	24	40	48
Net periodic pension cost	$ 17	$ 38	$ 34	$ 76