Retirement Plans - Other Postretirement Benefit Plan (Details) - Other Postretirement Benefits Plan [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
Service cost	$ 0	$ 1	$ 0	$ 1
Interest cost	30	43	60	85
Amortization of gain	(21)	(42)	(42)	(83)
Total expense, net	$ 9	$ 2	$ 18	$ 3