Commitments and Contingencies - Environmental (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Loss Contingencies [Line Items]
Accrued obligations for environmental matters, current liabilities	$ 75		$ 75
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	450	558	458	570
Accruals	(1)	(14)	(1)	(11)
Payments	(9)	(11)	(17)	(26)
Ending balance	440	533	440	533
Environmental Issue
Loss Contingencies [Line Items]
Site Contingency, Estimated Time Frame for Accrued Cost Distributions	10 years		10 years
Number of alleged environmental contamination sites (in sites)	242		242
Number of environmental superfund sites (in sites)	16		16
Liability for third-party tort claims	13		13
Future costs for environmental liabilities, minimum	330		330
Future costs for environmental liabilities, maximum	$ 610		$ 610