Income Taxes (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 280	$ (93)	$ 232
Effective tax rate (percent)	24.40%		25.10%
Tax reserves	673	669
Impact on tax expense if tax reserves were unnecessary	673
Accrued interest, related to income taxes in the balance sheet	200
Additional tax expense related to interest	1		1
Reasonably possible decrease in uncertain tax positions within the next 12 months, if a re-evaluation is required	38
Tax Litigation				593
Estimated additional income tax expense, litigation contingency	$ 100