Amortized Cost and Fair Value of Available for Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 28, 2013	Dec. 29, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 101,837	$ 90,995
Gross Unrealized Gains	861	1,414
Gross Unrealized Losses	415	7
Fair Value	102,283	92,402
Money market investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,172	2,865
Fair Value	1,172	2,865
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,436	2,175
Gross Unrealized Gains	25	73
Gross Unrealized Losses	73
Fair Value	4,388	2,248
Corporate bonds and direct obligations of government agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	77,439	69,173
Gross Unrealized Gains	798	1,294
Gross Unrealized Losses	332	6
Fair Value	77,905	70,461
U.S. Treasury Obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	18,790	16,782
Gross Unrealized Gains	38	47
Gross Unrealized Losses	10	1
Fair Value	$ 18,818	$ 16,828