Amortized Cost and Fair Value of Available for Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 28, 2014	Dec. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 102,800	$ 102,159
Gross Unrealized Gains	890	833
Gross Unrealized Losses	158	455
Fair Value	103,532	102,537
Money market investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,278	2,499
Fair Value	5,278	2,499
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,892	4,350
Gross Unrealized Gains	8	19
Gross Unrealized Losses	23	72
Fair Value	4,877	4,297
Corporate bonds and direct obligations of government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	73,118	76,786
Gross Unrealized Gains	853	783
Gross Unrealized Losses	128	370
Fair Value	73,843	77,199
U.S. Treasury Obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,512	18,524
Gross Unrealized Gains	29	31
Gross Unrealized Losses	7	13
Fair Value	$ 19,534	$ 18,542