Commitments and Contingencies - Environmental (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Loss Contingencies [Line Items]
Accrued obligations for environmental matters, current liabilities	$ 55
Site Contingency, Estimated Time Frame for Accrued Cost Distributions	10 years
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	435	458
Accruals	2	0
Payments	(10)	(8)
Ending balance	427	450
Environmental Issue
Loss Contingencies [Line Items]
Number of alleged environmental contamination sites (in sites)	241
Number of environmental superfund sites (in sites)	16
Liability for third-party tort claims	13
Future costs for environmental liabilities, minimum	320
Future costs for environmental liabilities, maximum	$ 590