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, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at the Beginning of Year	$ 783	$ 746
Unrecognized Loss (Gain)	24	22
Components of Net Periodic Postretirement Benefit Cost
Service Cost	41	42	$ 41
Interest Cost	29	26	28
Net Expected Benefit Payments	(63)	(53)
Obligation at End of Year	$ 814	$ 783	$ 746