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Significant Accounting Policies - Narrative (Details)
$ in Millions
6 Months Ended 12 Months Ended
Jul. 31, 2016
Jan. 29, 2017
USD ($)
Jan. 31, 2016
USD ($)
Jan. 25, 2015
USD ($)
Number of operating segments 5 4 5  
Restricted cash associated with various commitments   $ 5.3 $ 0.5  
Aggregate net investments under cost method of accounting   $ 27.1 20.2  
Other Intangible Assets and Long-lived Assets [Abstract]        
Percent of realizable undiscounted cash flows used to determine useful life of acquired finite-lived intangible assets, minimum   90.00%    
Sales and Marketing [Abstract]        
Advertising costs   $ 0.4 0.2 $ 0.1
Product Development and Engineering [Abstract]        
Recoveries from nonrecurring engineering services   $ 11.9 21.1 $ 29.3
Cash equivalents | Maximum        
Investment maturity period   90 days    
Other assets        
Aggregate net investments under cost method of accounting   $ 21.0    
Total equity method investments   $ 2.0 $ 1.1