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Contingencies and Commitments - Changes in Accrued Liabilities for Remediation Activities (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Change in Accrued Liabilities for Remediation Activities [Roll Forward]  
Beginning of period $ 212us-gaap_AccrualForEnvironmentalLossContingencies
Accruals for environmental remediation deemed probable and reasonably estimable 0us-gaap_AccrualForEnvironmentalLossContingenciesProvisionForNewLosses
Obligations settled (2)us-gaap_AccrualForEnvironmentalLossContingenciesPayments
End of period $ 210us-gaap_AccrualForEnvironmentalLossContingencies