Employee Benefit Plans (Schedule of Changes in Accumulated Postretirement Benefits Obligations) (Details) (Postretirement Medical and Life Benefit Plan, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Postretirement Medical and Life Benefit Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Obligation at Beginning of Year	$ 671	$ 691
Unrecognized Loss (Gain)	46	(33)
Components of Net Periodic Postretirement Benefit Cost
Service Cost	41	40	35
Interest Cost	28	23	24
Net Expected Benefit Payments	(40)	(50)
Obligation at End of Year	$ 746	$ 671	$ 691