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Debt - Convertible Senior Notes Due 2021 (Details)
3 Months Ended 9 Months Ended
Sep. 15, 2015
USD ($)
$ / shares
Oct. 27, 2018
USD ($)
Oct. 28, 2017
USD ($)
Oct. 24, 2015
trading_day
Oct. 27, 2018
USD ($)
Oct. 28, 2017
USD ($)
Jan. 27, 2018
USD ($)
Debt Instrument [Line Items]              
Amortization of debt discount         $ 14,223,000 $ 13,471,000  
0.75% Convertible Senior Notes Due 2021              
Debt Instrument [Line Items]              
Debt, interest rate (in percent)   0.75%     0.75%    
Debt intrument, conversion installments amount $ 1,000            
Debt instrument,conversion ratio 10.3211            
Debt instrument, face amount $ 485,000,000.0 $ 485,000,000     $ 485,000,000   $ 485,000,000
Debt instrument, convertible, conversion price (per share) | $ / shares $ 96.89            
Convertible debt, trading day threshold | trading_day       20      
Convertible debt, consecutive trading day threshold | trading_day       30      
Convertible debt, percentage of stock trigger price threshold       130.00%      
Debt instrument conversion trigger price | $ / shares $ 125.96            
Convertible debt, measurement period for percentage of product sale price of common stock and applicable conversion threshold       98.00%      
Convertible debt, comparable yield   5.50%          
Amortization of debt discount   $ 4,800,000 $ 4,500,000   14,200,000 $ 13,500,000  
Convertible Debt   417,835,000     417,835,000   402,249,000
Unamortized discount   60,676,000     60,676,000   74,899,000
Debt issuance cost   6,489,000     6,489,000   7,852,000
Standby Letters of Credit              
Debt Instrument [Line Items]              
Line of credit   $ 0     $ 0   $ 0