Fair Value (Details) (Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Jun. 29, 2012	Dec. 31, 2011
Cash equivalents [Member] | Money market funds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	$ 50,372	$ 62,131
Cash equivalents [Member] | Corporate bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	1,400
Cash equivalents [Member] | Level 1 [Member] | Money market funds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	50,372	62,131
Cash equivalents [Member] | Level 2 [Member] | Corporate bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	1,400
Cash equivalents [Member] | Level 3 [Member] | Money market funds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Cash equivalents [Member] | Level 3 [Member] | Corporate bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Short-term investments [Member] | State, municipal and local government agencies bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	44,671	38,825
Short-term investments [Member] | Corporate bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	22,513	18,604
Short-term investments [Member] | U.S. federal government bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	5,785	9,230
Short-term investments [Member] | Commercial paper [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	12,386	4,195
Short-term investments [Member] | Level 1 [Member] | U.S. federal government bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	5,785	9,230
Short-term investments [Member] | Level 2 [Member] | State, municipal and local government agencies bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	44,671	38,825
Short-term investments [Member] | Level 2 [Member] | Corporate bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	22,513	18,604
Short-term investments [Member] | Level 2 [Member] | Commercial paper [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	12,386	4,195
Short-term investments [Member] | Level 3 [Member] | State, municipal and local government agencies bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Short-term investments [Member] | Level 3 [Member] | Corporate bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Short-term investments [Member] | Level 3 [Member] | U.S. federal government bonds [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Short-term investments [Member] | Level 3 [Member] | Commercial paper [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Prepaids and other current assets [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	137,420	133,358
Prepaids and other current assets [Member] | Foreign exchange forward contracts[Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	293	373
Prepaids and other current assets [Member] | Level 1 [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	56,157	71,361
Prepaids and other current assets [Member] | Level 2 [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	81,263	61,997
Prepaids and other current assets [Member] | Level 2 [Member] | Foreign exchange forward contracts[Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value	293	373
Prepaids and other current assets [Member] | Level 3 [Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Prepaids and other current assets [Member] | Level 3 [Member] | Foreign exchange forward contracts[Member]
Financial assets measured at fair value on a recurring basis
Total assets measured and recorded at fair value
Accrued Liabilities [Member]
Financial assets measured at fair value on a recurring basis
Total liabilities measured and recorded at fair value	191	159
Accrued Liabilities [Member] | Foreign exchange forward contracts[Member]
Financial assets measured at fair value on a recurring basis
Total liabilities measured and recorded at fair value	191	159
Accrued Liabilities [Member] | Level 2 [Member]
Financial assets measured at fair value on a recurring basis
Total liabilities measured and recorded at fair value	191	159
Accrued Liabilities [Member] | Level 2 [Member] | Foreign exchange forward contracts[Member]
Financial assets measured at fair value on a recurring basis
Total liabilities measured and recorded at fair value	191	159
Accrued Liabilities [Member] | Level 3 [Member]
Financial assets measured at fair value on a recurring basis
Total liabilities measured and recorded at fair value
Accrued Liabilities [Member] | Level 3 [Member] | Foreign exchange forward contracts[Member]
Financial assets measured at fair value on a recurring basis
Total liabilities measured and recorded at fair value