Amortized Accumulated Other Comprehensive Income Into Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	$ 9
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss to be reclassified from accumulated other comprehensive income into net periodic benefit cost	$ (46)

Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration