Retirement Plans and Postretirement Medical Benefits (Target Asset Allocation) (Details)	Dec. 31, 2014	Dec. 31, 2013
United States
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%
Percent of Plan Assets	100.00%	100.00%
United States | U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	11.00%
Percent of Plan Assets	12.00%	16.00%
United States | Non-U.S. equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	11.00%
Percent of Plan Assets	9.00%	14.00%
United States | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	68.00%
Percent of Plan Assets	69.00%	60.00%
United States | Real estate
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	2.00%
Percent of Plan Assets	5.00%	4.00%
United States | Private equity
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	8.00%
Percent of Plan Assets	5.00%	6.00%
Foreign
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%
Percent of Plan Assets	100.00%	100.00%
Foreign | U.K. equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	30.00%
Percent of Plan Assets	28.00%	33.00%
Foreign | Non-U.K. equities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	30.00%
Percent of Plan Assets	29.00%	35.00%
Foreign | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	40.00%
Percent of Plan Assets	40.00%	31.00%
Foreign | Cash
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%
Percent of Plan Assets	3.00%	1.00%