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Fair Value of Option Granted (Detail) - Equity Option
9 Months Ended
Sep. 26, 2015
Sep. 27, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]    
Risk-free interest rate, minimum 0.80% 0.95%
Risk-free interest rate, maximum 1.09% 1.32%
Expected dividend yield 0.00% 0.00%
Expected option life 3 years  
Expected volatility, minimum 42.30% 42.50%
Expected volatility, maximum 48.50% 45.40%
Weighted-average expected volatility 43.10% 42.60%
Minimum    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Expected option life   3 years
Maximum    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Expected option life   4 years