Employee Benefit Plans (Components of Postretirement Benefit Expense) (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 Disclosure [Line Items]
Service Cost	$ 69	$ 50	$ 41
Interest Cost	34	29	29
Amortization of Unrecognized Net (Gain) Loss	32	8	6
Net Postretirement Benefit Expense	135	87	76
Net Gain (Loss) During Period Recognized in Other Comprehensive Income (Loss)	41	218	18
Total Recognized in Net Postretirement Benefit Expense and Other Comprehensive Income	$ 176	$ 305	$ 94