Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Total income tax expense using statutory U.S. federal income tax rate	$ 659	$ 605	$ 620
Statutory rate	35.00%	35.00%	35.00%
Tax benefits that, if recognized, would affect effective tax rate	34	27	28
Expense in interest and penalties related to unrecognized tax benefits	2	2	2
Accrued interest and penalties related to unrecognized tax benefits	19	16
Expected decrease in gross unrecognized tax benefits in next twelve months	$ 12