Post-retirement Plan (Net Periodic Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		5 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 1,093	$ 1,013	$ 2,596	$ 3,337
Interest cost on projected benefit obligations	556	556	1,424	1,698
Expected return on plan assets	(856)	(802)	(2,053)	(2,615)
Net periodic pension expense	793	767	$ 1,967	2,420
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	411	380		1,238	$ 1,106
Interest cost on projected benefit obligations	234	250		705	714
Amortization of prior service credit	(870)	(870)		(2,611)	(2,610)
Net periodic post-retirement credit	$ (225)	$ (240)		$ (668)	$ (790)