Financial Instruments - Gross Unrealized Gains and Losses on Available-For-Sale Investments (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 6,503	$ 5,069
Amortized Cost	6,405	5,042
Gross Unrealized, Gains	101	37
Gross Unrealized, Losses	(3)	(10)
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	168	1,029
Amortized Cost	168	1,029
Corporate notes and bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	3,705	2,032
Amortized Cost	3,650	2,024
Gross Unrealized, Gains	56	16
Gross Unrealized, Losses	(1)	(8)
U.S. government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	1,156	1,021
Amortized Cost	1,154	1,018
Gross Unrealized, Gains	2	3
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	648	292
Amortized Cost	644	292
Gross Unrealized, Gains	4	1
Gross Unrealized, Losses		(1)
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	334	223
Amortized Cost	334	223
Gross Unrealized, Gains	2	1
Gross Unrealized, Losses	(2)	(1)
Foreign government bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	72	72
Amortized Cost	71	72
Gross Unrealized, Gains	1
Other debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value		3
Amortized Cost		1
Gross Unrealized, Gains		2
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	420	397
Amortized Cost	384	383
Gross Unrealized, Gains	$ 36	$ 14

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details