Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Jun. 30, 2014
Income Tax Disclosure [Abstract]
Tax Litigation			$ 593
Estimated additional income tax expense, litigation contingency	100
Tax reserves	811			829
Impact on tax expense if tax reserves were unnecessary	811
Accrued interest, related to income taxes in the balance sheet	197
Additional tax expense related to interest	1	187
Reasonably possible decrease in uncertain tax positions within the next 12 months, if a re-evaluation is required	$ 204