Components of Pension Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of Prior Service Credits	$ (6)		$ (749)		$ (186)	$ (2,247)
Recognized Net Actuarial Loss	41		6,247		749	18,798
Total	35		5,498		563	16,551
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service Cost	54		96		247	289
Interest Cost	333		308		932	927
Amortization of Prior Service Credits	(6)		(93)		(187)	(279)
Recognized Net Actuarial Loss	59		390		806	1,176
Curtailment Gain	0	$ (416)	0		(416)	0
Total	$ 440		$ 701		$ 1,382	$ 2,113
Decrease in plan liabilities due to plan remeasurement				$ 2,235