Post-retirement Plan (Net Periodic Pension Expense) (Details) - 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 [Line Items]
Defined Benefit Plan, Service Cost	$ 1,209	$ 1,093	$ 3,605	$ 3,337
Interest cost on projected benefit obligations	450	556	1,325	1,698
Expected return on plan assets	(822)	(856)	(2,441)	(2,615)
Defined Benefit Plan, Amortization of Gain (Loss)	15	0	45	0
Net periodic pension expense	852	793	2,534	2,420
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	387	411	1,161	1,238
Interest cost on projected benefit obligations	267	234	801	705
Amortization of prior service credit	(870)	(870)	(2,611)	(2,611)
Defined Benefit Plan, Amortization of Gain (Loss)	22	0	66	0
Net periodic post-retirement credit	$ (238)	$ (225)	$ (715)	$ (668)