Commitments and Contingencies - Environmental (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Environmental Issue sites	Dec. 31, 2013 Environmental Issue
Loss Contingencies [Line Items]
Number of alleged environmental contamination sites (in sites)					237
Number of environmental superfund sites (in sites)					16
Liability for third-party tort claims					$ 14	$ 13
Accrued obligations for environmental matters, current liabilities	55		55
Future costs for environmental liabilities, minimum					310
Future costs for environmental liabilities, maximum					580
Site Contingency, Estimated Time Frame for Accrued Cost Distributions			10 years
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	427	450	435	458
Accruals	3	(1)	5	(1)
Payments	(14)	(9)	(24)	(17)
Ending balance	$ 416	$ 440	$ 416	$ 440