Fair Value Measurements - Maturity Dates of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 29, 2013	Dec. 31, 2012
Fair Value Measurements, Maturity Dates Of Investments [Line Items]
Amortized Cost	$ 398,997	$ 328,796
Estimated Fair Value	398,152	329,335
Less Than 1 Year [Member]
Fair Value Measurements, Maturity Dates Of Investments [Line Items]
Amortized Cost	143,924
Estimated Fair Value	144,074
1 to 5 Years [Member]
Fair Value Measurements, Maturity Dates Of Investments [Line Items]
Amortized Cost	246,137
Estimated Fair Value	245,725
6 to 10 Years [Member]
Fair Value Measurements, Maturity Dates Of Investments [Line Items]
Amortized Cost	8,936
Estimated Fair Value	8,353
Thereafter [Member]
Fair Value Measurements, Maturity Dates Of Investments [Line Items]
Amortized Cost	0
Estimated Fair Value	$ 0