Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2016		Jan. 25, 2015		Jan. 26, 2014
Notes to financial statements [Abstract]
SHIELD warranty charge	$ 26
Estimated product warranty liabilities
Balance at beginning of period	8	[1]	$ 8		$ 15
Additions	27		5		7
Deductions	(24)		(5)		(14)
Balance at end of period	$ 11	[1]	$ 8	[1]	$ 8

[1] Please refer to Note 10 of these Notes to the Consolidated Financial Statements for a discussion regarding warranties.