Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Liability for unrecognized tax benefits	$ 507		$ 507		$ 462
Unrecognized tax benefits, accrued interest	40		40		30
Unrecognized tax benefits that would impact effective tax rate	176		176		160
Interest expense related to taxing authority examinations	4	3
Reductions in interest expense related to taxing authority examinations			8	15
Interest expense related to taxing authority examinations, net of tax	2	2
Reductions in interest expense related to taxing authority examinations, net of tax			5	9
Provision for income taxes, reduction related primarily to resolutions for prior year examinations	$ 22		$ 22