Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 Plaintiff Cases site
Commitments And Contingent Liabilities [Line Items]
Number of cases administratively dismissed or inactive	100
Liable periods	20 years
Accrued environmental obligations approximately	$ 60
Sites associated with remediation	50
Remediation and related matters possible to estimate costs	$ 156
Currently not able to estimate a range of costs to sites	5
Number of cases pending	1,125
Number of Plaintiffs Involved in Pending Cases	1,643
Other Litigation [Member]
Commitments And Contingent Liabilities [Line Items]
Number of cases administratively dismissed or inactive	8,298