Unrecognized Tax Benefits and Related Accrued Estimated Interest and Penalties (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2013	Mar. 31, 2013
Income Taxes [Line Items]
Balance at December 31, 2012, unrecognized tax benefits		$ (972)
Activity for three months March, unrecognized tax benefits	6	99
Balance at March 31, 2013, unrecognized tax benefits	(867)
Balance at December 31, 2012, accrued estimated interest and tax penalties		(104)
Activity for three months ended March, accrued estimated interest and tax penalties	1	20
Balance at March 31, 2013, accrued estimated interest and tax penalties	$ (83)

This element represents the total of accruals as of the date of the statement of financial position for interest recognized 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 and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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This element represents the total of interest expense recognized 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 and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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