Fair Value Measurements - Summary of Short-Term and Long-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 29, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	$ 398,997	$ 328,796
Gross Unrealized Gains	498	1,038
Gross Unrealized Losses	(1,343)	(499)
Estimated Fair Value	398,152	329,335
U.S. Government and Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	100,275	83,499
Gross Unrealized Gains	22	33
Gross Unrealized Losses	(35)	0
Estimated Fair Value	100,262	83,532
Obligations of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	13,905	4,830
Gross Unrealized Gains	9	10
Gross Unrealized Losses	0	0
Estimated Fair Value	13,914	4,840
State and Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	109,106	96,383
Gross Unrealized Gains	102	161
Gross Unrealized Losses	(245)	(28)
Estimated Fair Value	108,963	96,516
Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	164,747	130,634
Gross Unrealized Gains	346	790
Gross Unrealized Losses	(1,058)	(468)
Estimated Fair Value	164,035	130,956
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	10,964	13,450
Gross Unrealized Gains	19	44
Gross Unrealized Losses	(5)	(3)
Estimated Fair Value	$ 10,978	$ 13,491