Investments - Narrative (Details) (USD $)	12 Months Ended
	Jan. 25, 2015	Jan. 26, 2014	Jan. 27, 2013
Investment [Line Items]
Investment in privately traded companies, cash consideration	$ 7,148,000	$ 2,500,000	$ 2,500,000
Minimum
Investment [Line Items]
Investment maturity period	3 months
Maximum
Investment [Line Items]
Investment maturity period	90 days
Temporary investments | Minimum
Investment [Line Items]
Investment maturity period	3 months
Temporary investments | Maximum
Investment [Line Items]
Investment maturity period	12 months
Long-term investments | Minimum
Investment [Line Items]
Investment maturity period	12 months
Other assets
Investment [Line Items]
Total equity investment in privately traded companies	$ 12,100,000	$ 5,000,000