Contingencies and Environmental Liabilities - Environmental Matters - Textual (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Loss Contingencies [Line Items]
Accrued liabilities for environmental matters	$ 145	$ 171
Aggregate possible expenditure on environmental matters	$ 112
Term for paying off environmental liabilities	15 years
Environmental Matters [Member]
Loss Contingencies [Line Items]
Number of plaintiffs filed amended complaint	2,200
Number of other defendants in environmental matters	12
Number of other defendants in Phase 1 trial	3
Number of plaintiffs selected to be reviewed	10
Plaintiffs dismissed claims	1,083