Post-retirement Plan (Net Periodic Pension Expense) (Details) - 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]
Defined Benefit Plan, Service Cost	$ 1,072	$ 1,198	$ 2,200	$ 2,397
Interest cost on projected benefit obligations	413	440	856	877
Expected return on plan assets	(976)	(811)	(2,009)	(1,621)
Amortization of (gain) loss	0	830	0	1,660
Net periodic pension expense	509	1,657	1,047	3,313
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	446	386	899	771
Interest cost on projected benefit obligations	233	266	471	531
Amortization of prior service credit	(870)	(870)	(1,741)	(1,741)
Amortization of (gain) loss	12	(22)	25	(44)
Net periodic post-retirement credit	$ (179)	$ (240)	$ (346)	$ (483)