Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reductions in interest related to taxing authority examinations	$ 53	$ 100	$ 69
Reductions in interest related to taxing authority examinations, net of tax	33	63	44
State net operating loss carryforwards	45
Liability for unrecognized tax benefits	426	494
Unrecognized tax benefits, accrued interest	14	62
Deferred tax assets, reductions	13	13
Unrecognized tax benefits that would impact effective tax rate	$ 125	$ 173
State and local jurisdiction [Member] \| Minimum [Member]
Net operating loss carryforwards, expiration date	2013
State and local jurisdiction [Member] \| Maximum [Member]
Net operating loss carryforwards, expiration date	2032

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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- Definition

The amount of the deferred tax liability which was not recognized because of the exceptions to comprehensive recognition of deferred taxes.

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- Definition

This element represents the amount of interest expense accrued as of the date of the statement of financial position for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity.

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