Changes in Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Oct. 31, 2013		Oct. 31, 2012	Oct. 31, 2013		Oct. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (212)			$ (211)
Other comprehensive income (loss) before reclassifications1	6	[1]		1	[2]
Amounts reclassified from AOCI	5			9
Net other comprehensive income (loss)	7		12	(5)		(1)
Net other comprehensive income (loss)	(10)		(9)	(4)		(1)
Net other comprehensive income (loss)	14		5	19		9
Net other comprehensive income (loss)	11		8	10		7
Ending balance	(201)			(201)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	6			0
Other comprehensive income (loss) before reclassifications1	(10)	[1]		(3)	[2]
Amounts reclassified from AOCI	0			(1)
Net other comprehensive income (loss)	(10)			(4)
Ending balance	(4)			(4)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	5			0
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(2)			10
Other comprehensive income (loss) before reclassifications1	7	[1]		(5)	[2]
Amounts reclassified from AOCI	0			0
Net other comprehensive income (loss)	7			(5)
Ending balance	5			5
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax	(2)			0
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(216)			(221)
Other comprehensive income (loss) before reclassifications1	9	[1]		9	[2]
Amounts reclassified from AOCI	5			10
Net other comprehensive income (loss)	14			19
Ending balance	(202)			(202)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	$ (5)			$ 0

[1] 1Net of tax benefit (cost) of $(2), $5, and $(5) related to currency translation adjustments, cash flow hedges, and postretirement benefits adjustments, respectively.

[2] 1Net of tax benefit (cost) of $(2), $2, and $(5) related to currency translation adjustments, cash flow hedges, and postretirement benefits adjustments, respectively.