Retirement Plans and Postretirement Medical Benefits (Target Asset Allocation) (Details)	Dec. 31, 2012	Dec. 31, 2011
UK Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	100.00%
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
UK Plan [Member] | UK Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	32.00%
Defined Benefit Plan, Actual Plan Asset Allocations	32.00%	34.00%
UK Plan [Member] | Non UK Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	33.00%
Defined Benefit Plan, Actual Plan Asset Allocations	31.00%	28.00%
UK Plan [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	35.00%
Defined Benefit Plan, Actual Plan Asset Allocations	36.00%	32.00%
UK Plan [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	0.00%
Defined Benefit Plan, Actual Plan Asset Allocations	1.00%	6.00%
United States Pension Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	100.00%
Defined Benefit Plan, Actual Plan Asset Allocations	100.00%	100.00%
United States Pension Plans of US Entity, Defined Benefit [Member] | US Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	14.00%
Defined Benefit Plan, Actual Plan Asset Allocations	14.00%	18.00%
United States Pension Plans of US Entity, Defined Benefit [Member] | Non US Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	14.00%
Defined Benefit Plan, Actual Plan Asset Allocations	15.00%	16.00%
United States Pension Plans of US Entity, Defined Benefit [Member] | Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	62.00%
Defined Benefit Plan, Actual Plan Asset Allocations	61.00%	56.00%
United States Pension Plans of US Entity, Defined Benefit [Member] | Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	2.00%
Defined Benefit Plan, Actual Plan Asset Allocations	4.00%	4.00%
United States Pension Plans of US Entity, Defined Benefit [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Weighted Target Asset Allocations	8.00%
Defined Benefit Plan, Actual Plan Asset Allocations	6.00%	6.00%