Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			$ (350)
Net other comprehensive income (loss)	$ (26)	$ (17)	(83)	$ (23)
Ending balance	(433)		(433)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(131)
Net other comprehensive income (loss)	(25)	(30)	(110)	(58)
Ending balance	(241)		(241)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			11
Net other comprehensive income (loss)	(7)	8	14	20
Ending balance	25		25
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance			(230)
Net other comprehensive income (loss)	6	$ 5	13	$ 15
Ending balance	$ (217)		$ (217)