Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 513	$ 572	$ 449
Other comprehensive (loss) income:
Foreign currency translation adjustment, net of tax of $(5), $(9), and $7 in 2010, 2011, and 2012, respectively	(55)	37	21
Amounts related to postretirement benefit plans:
Net actuarial (loss) gain and prior service cost, net of tax of $46, $(9), and $42 in 2010, 2011, and 2012, respectively	(67)	13	(66)
Reclassification to earnings, net of tax of $(2), $(8), and $(8) in 2010, 2011, and 2012, respectively	12	12	3
Amounts related to cash flow hedges:
Net (loss) gain on hedging instruments, net of tax of $7, $10, and $(3) in 2010, 2011, and 2012, respectively	6	(17)	(11)
Reclassification to earnings, net of tax of $(6) in 2010 and $(3) in 2012	5		10
Net other comprehensive (loss) income	(99)	45	(43)
Total comprehensive income	$ 414	$ 617	$ 406