Fair Value Measurements - Summary of Short-Term and Long-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 28, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	$ 402,351	$ 328,796
Gross Unrealized Gains	631	1,038
Gross Unrealized Losses	(853)	(499)
Estimated Fair Value	402,129	329,335
U.S. Government and Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	94,027	83,499
Gross Unrealized Gains	41	33
Gross Unrealized Losses	(4)	0
Estimated Fair Value	94,064	83,532
Obligations of Government-Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	34,116	4,830
Gross Unrealized Gains	6	10
Gross Unrealized Losses	0	0
Estimated Fair Value	34,122	4,840
State and Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	90,417	96,383
Gross Unrealized Gains	115	161
Gross Unrealized Losses	(88)	(28)
Estimated Fair Value	90,444	96,516
Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	173,900	130,634
Gross Unrealized Gains	456	790
Gross Unrealized Losses	(759)	(468)
Estimated Fair Value	173,597	130,956
Other Investments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized Cost	9,891	13,450
Gross Unrealized Gains	13	44
Gross Unrealized Losses	(2)	(3)
Estimated Fair Value	$ 9,902	$ 13,491