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Income Taxes - Additional information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Taxes
Effective income tax rate	21.30%	27.80%
Tax benefit associated with the U.S. Federal Research and Development Tax Credit	$ 4
Material discrete tax items reflected in the effective tax rate		0

- Definition

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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