Changes to Debt (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Debt Instrument [Line Items]
Debt maturing within one year, beginning balance	$ 4,369
Long-term debt, beginning balance	47,618
Total, beginning balance	51,987
Proceeds from long-term borrowings	500
Repayments of long-term borrowings and capital leases obligations	(73)	(1,828)
Increase (decrease) in short-term obligations, excluding current maturities	581	(1,734)
Other	(114)
Debt maturing within one year, ending balance	10,888
Long-term debt, ending balance	41,993
Total, ending balance	52,881
Long-term Debt
Debt Instrument [Line Items]
Long-term debt, beginning balance	47,618
Proceeds from long-term borrowings	500
Reclassifications of long-term debt	(6,008)
Other	(117)
Long-term debt, ending balance	41,993
Debt Maturing Within One Year
Debt Instrument [Line Items]
Debt maturing within one year, beginning balance	4,369
Repayments of long-term borrowings and capital leases obligations	(73)
Increase (decrease) in short-term obligations, excluding current maturities	581
Reclassifications of long-term debt	6,008
Other	3
Debt maturing within one year, ending balance	$ 10,888