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Organization and Summary of Significant Accounting Policies - Narrative - Concentrations of Risk (Details)
12 Months Ended
Dec. 31, 2017
Jan. 01, 2017
Dec. 31, 2017
Jan. 01, 2017
Jan. 03, 2016
Credit concentration risk [Member] | Investment portfolio [Member]          
Concentration Risk [Line Items]          
Maximum investment portfolio credit exposure     5.00%    
Credit concentration risk [Member] | Issue size [Member]          
Concentration Risk [Line Items]          
Maximum investment portfolio credit exposure     5.00%    
Industry credit concentration risk [Member] | Investment portfolio [Member]          
Concentration Risk [Line Items]          
Maximum investment portfolio credit exposure     30.00%    
Geographic concentration risk [Member] | Sales revenue, net [Member] | Outside the United States [Member]          
Concentration Risk [Line Items]          
Concentration percent     45.00% 46.00% 46.00%
Geographic concentration risk [Member] | Accounts receivable [Member] | Outside the United States [Member]          
Concentration Risk [Line Items]          
Concentration percent 48.00% 48.00%