Post-retirement Plan (Net Periodic Pension Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		5 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	$ 1,106	$ 944	$ 1,582	$ 2,235
Interest cost on projected benefit obligations	563	518	868	1,138
Expected Return on Plan Assets	(867)	(747)	(1,252)	(1,752)
Net periodic pension expense	802	715	$ 1,198	1,621
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	412	375		826	$ 726
Interest cost on projected benefit obligations	234	243		471	464
Amortization of prior service Credit	(870)	(870)		(1,741)	(1,740)
Net periodic post-retirement credit	$ (224)	$ (252)		$ (444)	$ (550)