Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Taxes [Line Items]
Effective income tax rate	32.10%	32.60%		32.10%	29.50%
Income tax expense (benefit) recognized due to retroactive provisions in American Taxpayer Relief Act of 2012			$ (3)
Unrecognized tax benefits	14			14
Unrecognized tax benefits, period increase (decrease)				(20)
Unrecognized tax benefits that, if recognized, would impact the effective tax rate	12			12
Net cash payments (receipts) for income tax (refunds)				54	37
US Federal Tax Issue
Income Taxes [Line Items]
Change in unrecognized tax benefits, amount of unrecorded benefit	$ 21			$ 21