Fair Value Measurements (Details) - USD ($) $ in Thousands		Jul. 04, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value		$ 228,479	$ 228,198
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net current assets and current liabilities, fair value		228,468	228,255
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net current assets and current liabilities, fair value		39,745	30,375
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net current assets and current liabilities, fair value		188,723	197,880
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net current assets and current liabilities, fair value		0	0
Commercial papers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value		9,997	9,998
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value		14,794	26,456
U.S. treasury bills and notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value		24,951	3,919
Securities and obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value		178,737	187,825
Reported Value Measurement [Member] | Commercial papers | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	9,997	9,998
Reported Value Measurement [Member] | Commercial papers | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | Commercial papers | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	9,997	9,998
Reported Value Measurement [Member] | Commercial papers | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | Money market funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	14,794	26,456
Reported Value Measurement [Member] | Money market funds | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	14,794	26,456
Reported Value Measurement [Member] | Money market funds | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | Money market funds | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | U.S. treasury bills and notes | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	24,951	3,919
Reported Value Measurement [Member] | U.S. treasury bills and notes | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	24,951	3,919
Reported Value Measurement [Member] | U.S. treasury bills and notes | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | U.S. treasury bills and notes | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | Securities and obligations of U.S. government agencies | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	178,737	187,825
Reported Value Measurement [Member] | Securities and obligations of U.S. government agencies | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | Securities and obligations of U.S. government agencies | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	178,737	187,825
Reported Value Measurement [Member] | Securities and obligations of U.S. government agencies | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Reported Value Measurement [Member] | Available-for-sale securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	228,479	228,198
Reported Value Measurement [Member] | Available-for-sale securities | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	39,745	30,375
Reported Value Measurement [Member] | Available-for-sale securities | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	188,734	197,823
Reported Value Measurement [Member] | Available-for-sale securities | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total, fair value	[1]	0	0
Designated as Hedging Instrument | Foreign Exchange Forward | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives, other current asset	[2]	1	61
Foreign currency derivatives, other current liabilities	[3]	(12)	(4)
Designated as Hedging Instrument | Foreign Exchange Forward | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives, other current asset	[2]	0	0
Foreign currency derivatives, other current liabilities	[3]	0	0
Designated as Hedging Instrument | Foreign Exchange Forward | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives, other current asset	[2]	1	61
Foreign currency derivatives, other current liabilities	[3]	(12)	(4)
Designated as Hedging Instrument | Foreign Exchange Forward | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency derivatives, other current asset	[2]	0	0
Foreign currency derivatives, other current liabilities	[3]	$ 0	$ 0

[1] Included in cash and cash equivalents and short-term investments on our condensed consolidated balance sheets. See “Investments” in Note 7 for further details.

[2] Included in other current assets on our condensed consolidated balance sheets. Consisted of forward foreign exchange contracts for Japanese yen. See “Derivative Instruments and Hedging” in Note 8 for further details.

[3] Included in other current liabilities on our condensed consolidated balance sheets. Consisted of forward foreign exchange contracts for Japanese yen. See “Derivative Instruments and Hedging” in Note 8 for further details.