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Tax - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Reconciliation Of Statutory Federal Tax Rate [Line Items]
Effective tax rate	30.30%	32.30%	31.10%	32.10%
U.S. federal statutory rate			35.00%
Unrecognized tax benefit	$ 127		$ 127
Material changes in unrecognized tax benefits	$ 0		$ 0

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate is the regular tax rate if there are alternative tax systems.

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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The net amount of all increases and decreases in unrecognized tax benefits for the period.

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