Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Tax portion of foreign currency translation adjustment	$ 1	$ 7	$ (9)
Net actuarial gain (loss) and prior service cost, tax	16	42	(9)
Amounts related to postretirement benefit plans:
Reclassification to earnings, tax	(15)	(8)	(8)
Amounts related to cash flow hedges:
Net (loss) gain on hedging instruments, tax	(4)	(3)	10
Reclassification to earnings, tax	$ 1	$ (3)	$ 0

Tax effect of the increase (decrease) in the value of the projected benefit obligation and the (increase) decrease in the value of the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption that has not been recognized in net periodic benefit cost.

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Tax effect, net of reclassification adjustments, of the change in the balance sheet adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency of the reporting entity. Also includes the following: gain (loss) on foreign currency forward exchange contracts; foreign currency transactions designated as hedges of net investment in a foreign entity and intercompany foreign currency transactions that are of a long-term nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements; and gain (loss) on a derivative instrument or nonderivative financial instrument that may give rise to a foreign currency transaction gain (loss) that has been designated and qualified as a hedging instrument for hedging of the foreign currency exposure of a net investment in a foreign operation.

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- Definition

Tax effect of the income statement impact of the reclassification adjustment of accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges realized in net income. Also includes reclassification adjustments of an entity's share of an equity investee's deferred hedging gain (loss) realized in net income.

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- Definition

Tax effect of the change in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Also includes an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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