Cash, Cash Equivalents And Short Term Investments (Detail) - USD ($) $ in Thousands	Apr. 01, 2016	Jan. 01, 2016
Fair Value Measurements [Line Items]
Amortized Cost	$ 155,014	$ 171,699
Unrealized Gains	34	1
Unrealized Losses	(1)	(107)
Estimated Fair Value	155,047	171,593
U.S. Agency Securities
Fair Value Measurements [Line Items]
Amortized Cost	53,964	41,946
Unrealized Gains	33	1
Unrealized Losses	(1)	(106)
Estimated Fair Value	53,996	41,841
Cash
Fair Value Measurements [Line Items]
Amortized Cost	86,507	115,221
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	86,507	115,221
Money market securities
Fair Value Measurements [Line Items]
Amortized Cost	12,028	10,530
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	12,028	10,530
Total cash equivalents
Fair Value Measurements [Line Items]
Amortized Cost	12,028	10,530
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	12,028	10,530
Total cash and cash equivalents
Fair Value Measurements [Line Items]
Amortized Cost	98,535	125,751
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	98,535	125,751
State and municipal bonds
Fair Value Measurements [Line Items]
Amortized Cost	2,515	4,002
Unrealized Gains	1	0
Unrealized Losses	0	(1)
Estimated Fair Value	2,516	4,001
Total short-term investments
Fair Value Measurements [Line Items]
Amortized Cost	56,479	45,948
Unrealized Gains	34	1
Unrealized Losses	(1)	(107)
Estimated Fair Value	$ 56,512	$ 45,842