Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 25, 2015	Oct. 26, 2014	Oct. 25, 2015	Oct. 26, 2014	Jan. 25, 2015
Amortizable intangible assets components
Amortization expense	$ 18	$ 19	$ 56	$ 58
Future amortization expense associated with intangible assets
Remainder of fiscal 2016	19		19
Fiscal 2017	63		63
Fiscal 2018	50		50
Fiscal 2019	22		22
Fiscal 2020	13		13
Fiscal 2021 and beyond	5		5
Acquisition-related intangible assets
Amortizable intangible assets components
Gross Carrying Amount	193		193		$ 189
Accumulated Amortization	(148)		(148)		(134)
Net Carrying Amount	45		45		55
Patents and Licensed Technology
Amortizable intangible assets components
Gross Carrying Amount	451		451		449
Accumulated Amortization	(324)		(324)		(282)
Net Carrying Amount	127		127		167
Total intangible assets
Amortizable intangible assets components
Gross Carrying Amount	644		644		638
Accumulated Amortization	(472)		(472)		(416)
Net Carrying Amount	$ 172		$ 172		$ 222