Employee Benefit Plans (Components of Postretirement Benefit Expense) (Details) - Postretirement Medical and Life Benefit Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 41	$ 42	$ 41
Interest Cost	29	26	28
Amortization of Unrecognized Net (Gain) Loss	6	5	0
Net Postretirement Benefit Expense	76	73	69
Net (Gain) Loss During Period Recognized in Other Comprehensive Income (Loss)	18	17	46
Total Recognized in Net Postretirement Benefit Expense and Other Comprehensive Income	$ 94	$ 90	$ 115