Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 29, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	$ 174,897	$ 166,392
Total liabilities measured and recorded at fair value	63	143
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	72,375	59,931
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	102,522	106,461
Total liabilities measured and recorded at fair value	63	143
Cash equivalents [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	62,370	54,923
Cash equivalents [Member] | U.S. federal government bonds [Member] | Maturity less than 90 days [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	2,002	3,005
Cash equivalents [Member] | Corporate bonds [Member] | Maturity less than 90 days [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		3,614
Cash equivalents [Member] | Level 1 [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	62,370	54,923
Cash equivalents [Member] | Level 1 [Member] | U.S. federal government bonds [Member] | Maturity less than 90 days [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	2,002	3,005
Cash equivalents [Member] | Level 2 [Member] | Corporate bonds [Member] | Maturity less than 90 days [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		3,614
Short-term investments [Member] | U.S. federal government bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	8,003	2,003
Short-term investments [Member] | Certificates of deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	1,605	1,603
Short-term investments [Member] | State, municipal and local government agencies bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	59,191	59,050
Short-term investments [Member] | Corporate bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	31,047	31,562
Short-term investments [Member] | Commercial paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	9,944	10,288
Short-term investments [Member] | Level 1 [Member] | U.S. federal government bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	8,003	2,003
Short-term investments [Member] | Level 2 [Member] | Certificates of deposit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	1,605	1,603
Short-term investments [Member] | Level 2 [Member] | State, municipal and local government agencies bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	59,191	59,050
Short-term investments [Member] | Level 2 [Member] | Corporate bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	31,047	31,562
Short-term investments [Member] | Level 2 [Member] | Commercial paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	9,944	10,288
Prepaids and other current assets [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	735	344
Prepaids and other current assets [Member] | Level 2 [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	735	344
Accrued liabilities [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total liabilities measured and recorded at fair value	63	143
Accrued liabilities [Member] | Level 2 [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total liabilities measured and recorded at fair value	$ 63	$ 143