Amortized Cost, Unrealized Gains and Losses, and Fair Value of Available-for-sale Securities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Available-For-Sale Amortized Cost	$ 3,957	$ 1,925
Available-For-Sale Gross Unrealized Gains	4	0
Available-For-Sale Gross Unrealized Losses	(1)	0
Available-For-Sale Fair Value	3,960	1,925
Less: current portion of available-for-sale investment securities	(677)	(1,214)
Long-term available-for-sale investment securities	3,283	711
Debt Securities \| US Treasury securities
Available-For-Sale Amortized Cost	1,065	350
Available-For-Sale Gross Unrealized Gains	1
Available-For-Sale Fair Value	1,066	350
Debt Securities \| US Government-sponsored agency debt securities
Available-For-Sale Amortized Cost	2,818	1,568
Available-For-Sale Gross Unrealized Gains	3
Available-For-Sale Fair Value	2,821	1,568
Debt Securities \| Corporate Debt Securities
Available-For-Sale Amortized Cost	63
Available-For-Sale Fair Value	63
Debt and Equity Securities \| Auction Rate Securities
Available-For-Sale Amortized Cost	11	7
Available-For-Sale Gross Unrealized Losses	(1)
Available-For-Sale Fair Value	10	7
Available for sale Securities Current
Less: current portion of available-for-sale investment securities	$ (677)	$ (1,214)

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

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

- Definition

Investments in debt and equity securities which are categorized neither as trading securities nor held-to-maturity securities and which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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+ 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

- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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+ Details