Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Jan. 25, 2015	Jan. 26, 2014	Jan. 27, 2013	Jan. 29, 2012
Accounting Policies [Abstract]
Advertising Expense	$ 14,600,000	$ 13,100,000	$ 9,200,000
Foreign Currency Transaction Gain (Loss), Realized	500,000	4,700,000	(1,500,000)
Deferred Tax Assets, Valuation Allowance	(260,985,000)	(244,487,000)
Excess Tax Benefit Related To Stock Based Compensation	411,900,000
Cash and cash equivalents	496,654,000	1,151,587,000	732,786,000	667,876,000
Accounts receivable from significant customers (in percent)	30.00%	23.00%
Asset Retirement Obligation	7,400,000	11,100,000
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	4,412,977,000	4,087,893,000
Money Market Funds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 132,495,000	$ 307,865,000