Post-retirement Plan (Net Periodic Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 1,198	$ 1,106	$ 2,397	$ 2,235
Interest cost on projected benefit obligations	440	563	877	1,138
Expected return on plan assets	(811)	(867)	(1,621)	(1,752)
Defined Benefit Plan, Amortization of Gain (Loss)	(830)	0	(1,660)	0
Net periodic pension expense	1,657	802	3,313	1,621
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	386	412	771	826
Interest cost on projected benefit obligations	266	234	531	471
Amortization of prior service credit	(870)	(870)	(1,741)	(1,741)
Defined Benefit Plan, Amortization of Gain (Loss)	(22)	0	(44)	0
Net periodic post-retirement credit	$ (240)	$ (224)	$ (483)	$ (444)