Pension Plans and Postretirement Benefit Plan (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	$ 0	$ 0	$ 0	$ 0
Interest Cost	1,093	1,041	2,187	2,082
Expected Return on Plan Assets	(1,249)	(1,282)	(2,498)	(2,564)
Amortization of Prior Service Credit	0	0	0	0
Amortization of Net Actuarial Losses (Gains)	484	498	968	996
Net Periodic Benefit Cost	328	257	657	514
Employer Contributions	100		200
Estimated Future Employer Contributions in Current Fiscal Year	500		500
Postretirement Benefits
Net periodic benefit cost for pension plans and the postretirement benefit plan
Service Cost	117	115	235	230
Interest Cost	257	236	515	471
Expected Return on Plan Assets	0	0	0	0
Amortization of Prior Service Credit	(72)	(142)	(144)	(284)
Amortization of Net Actuarial Losses (Gains)	(78)	(62)	(156)	(124)
Net Periodic Benefit Cost	224	$ 147	450	$ 293
Employer Contributions	300		600
Estimated Future Employer Contributions in Current Fiscal Year	$ 900		$ 900