Pension Plans and Postretirement Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	$ 0	$ 0
Interest Cost	1,094	1,041
Expected Return on Plan Assets	(1,249)	(1,282)
Amortization of Prior Service Credit	0	0
Amortization of Net Actuarial Losses (Gains)	484	498
Net Periodic Benefit Cost	329	257
Employer Contributions	100
Estimated Future Employer Contributions in Current Fiscal Year	500
Postretirement Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	118	115
Interest Cost	258	235
Expected Return on Plan Assets	0	0
Amortization of Prior Service Credit	(72)	(142)
Amortization of Net Actuarial Losses (Gains)	(78)	(62)
Net Periodic Benefit Cost	226	$ 146
Employer Contributions	300
Estimated Future Employer Contributions in Current Fiscal Year	$ 900