Fair Value Measurements - Summary of Short-Term and Long-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 28, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	$ 457,698	$ 353,109
Gross Unrealized Gains	977	582
Gross Unrealized Losses	(443)	(723)
Estimated Fair Value	458,232	352,968
U.S. Government and Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	161,385	89,617
Gross Unrealized Gains	86	27
Gross Unrealized Losses	0	(18)
Estimated Fair Value	161,471	89,626
Obligations of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	27,294	33,506
Gross Unrealized Gains	4	5
Gross Unrealized Losses	0	(1)
Estimated Fair Value	27,298	33,510
State and Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	53,736	51,573
Gross Unrealized Gains	124	82
Gross Unrealized Losses	(2)	(28)
Estimated Fair Value	53,858	51,627
Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	194,064	166,642
Gross Unrealized Gains	734	453
Gross Unrealized Losses	(439)	(675)
Estimated Fair Value	194,359	166,420
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	21,219	11,771
Gross Unrealized Gains	29	15
Gross Unrealized Losses	(2)	(1)
Estimated Fair Value	$ 21,246	$ 11,785