Retirement Plans - Other Postretirement Benefit Plan (Details) - Other Postretirement Benefits Plan [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure
Service cost	$ 0	$ 0	$ 1	$ 1
Interest cost	42	39	127	117
Amortization of gain	(42)	(11)	(125)	(34)
(Income) expense, net	$ 0	$ 28	$ 3	$ 84