Employee Benefit Plans (Schedule of Changes in Accumulated Postretirement Benefits Obligations) (Details) - Postretirement Medical and Life Benefit Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at the Beginning of Year	$ 1,061	$ 814
Unrecognized Loss (Gain)	74	226
Components of Net Periodic Postretirement Benefit Cost
Service Cost	69	50	$ 41
Interest Cost	34	29	29
Net Expected Benefit Payments	(84)	(58)
Obligation at End of Year	$ 1,154	$ 1,061	$ 814