Expected Future Minimum Benefit Payments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Schedule of Postemployment Expected Future Benefit Payments [Line Items]
2014	$ 83
2015	86
2016	88
2017	89
2018	92
2019 - 2023	485
Defined Benefit Plan, Expected Future Benefit Payment, Total	923
Pension Benefits
Schedule of Postemployment Expected Future Benefit Payments [Line Items]
2014	69
2015	71
2016	73
2017	74
2018	76
2019 - 2023	404
Defined Benefit Plan, Expected Future Benefit Payment, Total	767
Other Postretirement Benefit Payments Gross
Schedule of Postemployment Expected Future Benefit Payments [Line Items]
2014	15
2015	16
2016	16
2017	16
2018	17
2019 - 2023	83
Defined Benefit Plan, Expected Future Benefit Payment, Total	163
Less Medicare Drug Subsidy
Schedule of Postemployment Expected Future Benefit Payments [Line Items]
2014	1
2015	1
2016	1
2017	1
2018	1
2019 - 2023	2
Defined Benefit Plan, Expected Future Benefit Payment, Total	$ 7