Employee Benefit Plans (Schedule of Assumptions used to Determine Net Periodic Cost and Benefit Obligations) (Details) (Postretirement Medical and Life Benefit Plan)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Postretirement Medical and Life Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	3.62%	4.31%	3.41%