The amounts in accumulated other comprehensive income related to gains and losses that are not recognized immediately and are expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Defined-benefit plan, amortization of net actuarial loss in 2013	$ 116,000,000
Defined-benefit plan, amortization of net prior service cost in 2013	1,000,000
Defined-benefit plan, health care cost trend rate assumed for next fiscal year	8.00%	9.00%
Defined-benefit plan, ultimate health care cost trend rate	5.00%
Defined benefit plan, amount of employer securities included in plan assets	0
Defined-contribution plans, recognized expense	55,000,000	41,000,000	40,000,000
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined-benefit plan, target asset-allocation range, minimum	45.00%
Defined-benefit plan, target asset-allocation range, maximum	55.00%
Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined-benefit plan, target asset-allocation range, minimum	20.00%
Defined-benefit plan, target asset-allocation range, maximum	30.00%
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined-benefit plan, target asset-allocation range, maximum	25.00%
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	107,000,000	311,000,000
Pension Plans, Defined Benefit [Member] \| Funded Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	101,000,000
Expected employer contributions in 2013	81,000,000
Pension Plans, Defined Benefit [Member] \| Unfunded Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	6,000,000
Expected employer contributions in 2013	45,000,000
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	19,000,000	17,000,000
Other Postretirement Benefit Plans, Defined Benefit [Member] \| Unfunded Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	19,000,000
Expected employer contributions in 2013	$ 16,000,000