Short-Term Investments - Summary of Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 28, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 78,483	$ 104,470
Gross Unrealized Gains	37	50
Gross Unrealized Losses	(42)	(14)
Total short-term investments, Estimated Fair Value	78,478	104,506
Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	1,607	1,603
Gross Unrealized Gains
Gross Unrealized Losses
Total short-term investments, Estimated Fair Value	1,607	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	41,565	59,009
Gross Unrealized Gains	36	45
Gross Unrealized Losses	(4)	(4)
Total short-term investments, Estimated Fair Value	41,597	59,050
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	25,459	31,568
Gross Unrealized Gains	1	4
Gross Unrealized Losses	(35)	(10)
Total short-term investments, Estimated Fair Value	25,425	31,562
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	3,846	10,287
Gross Unrealized Gains		1
Gross Unrealized Losses
Total short-term investments, Estimated Fair Value	3,846	10,288
U.S. federal government bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	6,006	2,003
Gross Unrealized Gains
Gross Unrealized Losses	(3)
Total short-term investments, Estimated Fair Value	$ 6,003	$ 2,003