Short-Term Investments - Summary of Short-Term Investments (Detail) - USD ($) $ in Thousands	Oct. 02, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 25,986	$ 31,845
Gross Unrealized Gains	16	19
Gross Unrealized Losses	(12)	(17)
Total short-term investments, Estimated Fair Value	25,990	31,847
State, municipal and local government agencies bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	2,502	13,946
Gross Unrealized Gains	1	16
Gross Unrealized Losses	0	(1)
Total short-term investments, Estimated Fair Value	2,503	13,961
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	23,484	17,899
Gross Unrealized Gains	15	3
Gross Unrealized Losses	(12)	(16)
Total short-term investments, Estimated Fair Value	$ 23,487	$ 17,886