Short-Term Investments - Summary of Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 29, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 109,751	$ 104,470
Gross Unrealized Gains	64	50
Gross Unrealized Losses	(25)	(14)
Total short-term investments, Estimated Fair Value	109,790	104,506
Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	1,605	1,603
Gross Unrealized Gains
Gross Unrealized Losses
Total short-term investments, Estimated Fair Value	1,605	1,603
State, municipal and local government agencies bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	59,137	59,009
Gross Unrealized Gains	56	45
Gross Unrealized Losses	(2)	(4)
Total short-term investments, Estimated Fair Value	59,191	59,050
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	31,062	31,568
Gross Unrealized Gains	7	4
Gross Unrealized Losses	(22)	(10)
Total short-term investments, Estimated Fair Value	31,047	31,562
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	9,944	10,287
Gross Unrealized Gains		1
Gross Unrealized Losses
Total short-term investments, Estimated Fair Value	9,944	10,288
U.S. federal government bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	8,003	2,003
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)
Total short-term investments, Estimated Fair Value	$ 8,003	$ 2,003