Pension and Other Postretirement Benefits (Funded Status of Pension Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Pension plans that have assets in excess of their accumulated benefit obligations with those whose assets are less than their obligations
Plans with assets in excess of accumulated benefit obligation, Plan Assets	$ 52	$ 52
Plans with accumulated benefit obligation in excess of assets, Plan Assets	553	521
Total, Plan Assets	605	573
Plans with assets in excess of accumulated benefit obligation, Accumulated Benefit Obligation	49	48
Plans with accumulated benefit obligation in excess of assets, Accumulated Benefit Obligation	640	647
Total, Accumulated Benefit Obligation	689	695
Plans with assets in excess of accumulated benefit obligation, Projected Benefit Obligation	50	50
Plans with accumulated benefit obligation in excess of assets, Projected Benefit Obligation	735	733
Pension Benefits [Member]
Pension plans that have assets in excess of their accumulated benefit obligations with those whose assets are less than their obligations
Total, Plan Assets	605	573	508
Total, Projected Benefit Obligation	785	783	727
Medical and Life Insurance Benefits [Member]
Pension plans that have assets in excess of their accumulated benefit obligations with those whose assets are less than their obligations
Total, Plan Assets	0	0
Total, Projected Benefit Obligation	$ 69	$ 74	$ 62