Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Jan. 31, 2016	Oct. 25, 2015	Jul. 26, 2015	Apr. 26, 2015	Jan. 25, 2015	Oct. 26, 2014	Jul. 27, 2014	Apr. 27, 2014	Jan. 31, 2016	Jan. 25, 2015	Jan. 26, 2014
Notes to financial statements [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	1.00%								1.00%
Debt Instrument, Convertible, Conversion Price	$ 20.1204								$ 20.1204		$ 20.1630
Warrant Strike Price									$ 27.0851		$ 27.1425
Numerator:
Net income	$ 207	$ 247	$ 26	$ 134	$ 193	$ 173	$ 128	$ 137	$ 614	$ 631	$ 440
Denominator:
Denominator for basic net income per share, weighted average shares (in shares)									543	552	588
Effect of dilutive securities:
Equity awards outstanding (in shares)									13	11	7
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities									13	0	0
Denominator for diluted net income per share, weighted average shares (in shares)									569	563	595
Net income per share:
Basic net income per share	$ 0.38	$ 0.45	$ 0.05	$ 0.24	$ 0.35	$ 0.32	$ 0.23	$ 0.24	$ 1.13	$ 1.14	$ 0.75
Diluted net income per share	$ 0.35	$ 0.44	$ 0.05	$ 0.24	$ 0.35	$ 0.31	$ 0.22	$ 0.24	$ 1.08	$ 1.12	$ 0.74
Anti-dilutive common equivalent shares from stock options and RSUs (in shares)									10	12	26