Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jul. 31, 2016	Jul. 26, 2015	Jul. 31, 2016	Jul. 26, 2015
Numerator:
Net income		$ 253	$ 26	$ 449	$ 160
Denominator:
Basic weighted average shares		534	541	536	545
Effect of dilutive securities:
Equity awards outstanding		23	11	20	13
1% Convertible Senior Notes		43	4	37	5
Warrants issued with the Notes		31	0	24	0
Diluted weighted average shares		631	556	617	563
Net income per share:
Basic net income per share	[1]	$ 0.47	$ 0.05	$ 0.84	$ 0.29
Diluted net income per share	[2]	$ 0.40	$ 0.05	$ 0.73	$ 0.28
Equity awards excluded from diluted net income per share because their effect would have been anti-dilutive		0	1	4	4
Debt Instrument, Interest Rate, Stated Percentage		1.00%		1.00%
Note Hedges Strike Price		$ 20.0877		$ 20.0877
Debt Instrument, Convertible, Conversion Price		20.0877		20.0877
Warrant Strike Price		27.0411
Average stock price		$ 46.57		$ 39.69

[1] Calculated as net income divided by basic weighted average shares.

[2] Calculated as net income divided by diluted weighted average shares.