Financial Instruments - Investments in Debt Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Held-to-maturity debt securities maturities total	$ 1,470	[1],[2]	$ 1,513	[1],[2]
Debt securities maturities within 1 year	33,167
Debt securities maturities over 1 to 5 years	10,286
Debt securities maturities over 5 to 10 years	1,828
Total debt securities	45,281
Certificates of deposit and other [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Held-to-maturity debt securities maturities within 1 year	1,173
Held-to-maturity debt securities with maturities over 1 to 5 years	296
Held-to-maturity debt securities maturities over 5 to 10 years	1
Held-to-maturity debt securities maturities total	1,470
Western European, Asian and other government debt [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	19,028	[3]
Available-for-sale debt securities maturities over 1 to 5 years	2,076	[3]
Available-for-sale debt securities maturities over 5 to 10 years	0	[3]
Available-for-sale debt securities maturities total	21,104	[3]
Corporate debt [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	2,165	[4]
Available-for-sale debt securities maturities over 1 to 5 years	4,205	[4]
Available-for-sale debt securities maturities over 5 to 10 years	1,612	[4]
Available-for-sale debt securities maturities total	7,982	[4]
Western European, Scandinavian and other government agency debt [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	3,176	[3]
Available-for-sale debt securities maturities over 1 to 5 years	433	[3]
Available-for-sale debt securities maturities over 5 to 10 years	0	[3]
Available-for-sale debt securities maturities total	3,609	[3]
Federal Home Loan Mortgage Corporation and Federal National Mortgage Association asset-backed securities [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	0
Available-for-sale debt securities maturities over 1 to 5 years	2,489
Available-for-sale debt securities maturities over 5 to 10 years	178
Available-for-sale debt securities maturities total	2,667
U.S. government debt [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	4,023
Available-for-sale debt securities maturities over 1 to 5 years	99
Available-for-sale debt securities maturities over 5 to 10 years	37
Available-for-sale debt securities maturities total	4,159
Supranational debt [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	1,979	[3]
Available-for-sale debt securities maturities over 1 to 5 years	688	[4]
Available-for-sale debt securities maturities over 5 to 10 years	0	[3]
Available-for-sale debt securities maturities total	2,667	[3]
Reverse repurchase agreements [Member]
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Available-for-sale debt securities maturities within 1 year	1,623	[5]
Available-for-sale debt securities maturities over 1 to 5 years	0	[4]
Available-for-sale debt securities maturities over 5 to 10 years	0	[4]
Available-for-sale debt securities maturities total	$ 1,623	[5]

[1] Gross unrealized gains and losses are not significant.

[2] The differences between the estimated fair values and carrying values of held-to-maturity debt securities, private equity securities at cost and short-term borrowings not measured at fair value on a recurring basis were not significant as of March 31, 2013 or December 31, 2012. The fair value measurements of our held-to-maturity debt securities and our short-term borrowings are based on Level 2 inputs, using a market approach. The fair value measurements of our private equity securities at cost are based on Level 3 inputs, using a market approach.

[3] All issued by above-investment-grade governments, government agencies or supranational entities, as applicable.

[4] Largely issued by above-investment-grade institutions in the financial services sector.

[5] Involving U.S. and U.K. government securities.