Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended						9 Months Ended
	May 01, 2019	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Jan. 31, 2020	Jan. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (363)			$ (363)				$ (363)
Adoption of ASU 2018-02 (Note 1)	(43)
Net other comprehensive income (loss)		$ 8	$ 7	(1)	$ 5	$ (1)	$ 14	14	$ 18
Ending balance		(392)						(392)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(207)			(207)				(207)
Adoption of ASU 2018-02 (Note 1)	(1)
Net other comprehensive income (loss)		6			18			3	(21)
Ending balance		(205)						(205)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	31			31				31
Adoption of ASU 2018-02 (Note 1)	(1)
Net other comprehensive income (loss)		(1)			(8)			1	37
Ending balance		31						31
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(187)			(187)				(187)
Adoption of ASU 2018-02 (Note 1)	(41)
Net other comprehensive income (loss)		3			(5)			10	$ 2
Ending balance		(218)						$ (218)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Adoption of ASU 2018-02 (Note 1)	$ (43)
Net other comprehensive income (loss)		$ 8	$ 7	$ (1)	$ 5	$ (1)	$ 14