Schedule of Unrealized Loss on Available for Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 27, 2014	Dec. 28, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	$ 15,916	$ 26,355
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	72	455
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	14,590
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	212
Available-for-sale investments with unrealized losses, Fair Value, Total	30,506	26,355
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	284	455
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	2,652	3,429
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	13	72
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	2,445
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	42
Available-for-sale investments with unrealized losses, Fair Value, Total	5,097	3,429
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	55	72
Corporate bonds and direct obligations of government agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	13,264	22,169
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	59	370
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	11,385
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	162
Available-for-sale investments with unrealized losses, Fair Value, Total	24,649	22,169
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	221	370
U.S. Treasury Obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value		757
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss		13
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	760
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	8
Available-for-sale investments with unrealized losses, Fair Value, Total	760	757
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	$ 8	$ 13