Changes in Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Apr. 30, 2014 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Jul. 31, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Apr. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Jul. 31, 2014 Accumulated Translation Adjustment [Member]	Apr. 30, 2014 Accumulated Translation Adjustment [Member]	Jul. 31, 2013 Accumulated Translation Adjustment [Member]	Apr. 30, 2013 Accumulated Translation Adjustment [Member]	Jul. 31, 2014 Accumulated Defined Benefit Plans Adjustment [Member]	Apr. 30, 2014 Accumulated Defined Benefit Plans Adjustment [Member]	Jul. 31, 2013 Accumulated Defined Benefit Plans Adjustment [Member]	Apr. 30, 2013 Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (188)	$ (211)	$ 1	$ (4)	$ 6	$ 0	$ (10)	$ 6	$ (2)	$ 10	$ (186)	$ (190)	$ (216)	$ (221)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(16)	(12)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	5	6
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent	4	5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(7)	(1)
Ending balance	$ (195)	$ (212)	$ 1	$ (4)	$ 6	$ 0	$ (10)	$ 6	$ (2)	$ 10	$ (186)	$ (190)	$ (216)	$ (221)