Short-Term Investments - Summary of Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 27, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 75,920	$ 104,470
Gross Unrealized Gains	60	50
Gross Unrealized Losses	(14)	(14)
Total short-term investments, Estimated Fair Value	75,966	104,506
Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		1,603
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Total short-term investments, Estimated Fair Value		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	36,195	59,009
Gross Unrealized Gains	41	45
Gross Unrealized Losses	(3)	(4)
Total short-term investments, Estimated Fair Value	36,233	59,050
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	32,376	31,568
Gross Unrealized Gains	16	4
Gross Unrealized Losses	(11)	(10)
Total short-term investments, Estimated Fair Value	32,381	31,562
Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	3,348	10,287
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Total short-term investments, Estimated Fair Value	3,348	10,288
U.S. federal government bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	4,001	2,003
Gross Unrealized Gains	3	0
Gross Unrealized Losses	0	0
Total short-term investments, Estimated Fair Value	$ 4,004	$ 2,003