Schedule II - Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2012
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 9		$ 9		$ 18
Additions Charged to Costs and Expenses	0		2		0
Additions Charged to Other Accounts	0		0		0
Deductions	0	[1]	2	[1]	9
Balance at End of Period	$ 9		$ 9		$ 9

[1] Doubtful accounts written off, net of recoveries.