Fair Value of Option Granted (Detail) - Equity Option	6 Months Ended
	Jun. 27, 2015	Jun. 28, 2014
Fair Value, Option, Quantitative Disclosures [Line Items]
Risk-free interest rate, minimum	0.80%	1.18%
Risk-free interest rate, maximum	1.09%	1.32%
Expected dividend yield	0.00%	0.00%
Expected option life	3 years	4 years
Expected volatility, minimum	42.30%	42.50%
Expected volatility, maximum	48.50%	44.10%
Weighted-average expected volatility	43.20%	42.50%