Schedule of Unrealized Loss on Available for Sale Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 28, 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	$ 9,572	$ 26,355
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	9	455
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	14,682
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	149
Available-for-sale investments with unrealized losses, Fair Value, Total	24,254	26,355
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	158	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	1,010	3,429
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	2	72
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	2,469
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	21
Available-for-sale investments with unrealized losses, Fair Value, Total	3,479	3,429
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	23	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	5,562	22,169
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	7	370
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	11,451
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	121
Available-for-sale investments with unrealized losses, Fair Value, Total	17,013	22,169
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	128	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	3,000	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	762
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	7
Available-for-sale investments with unrealized losses, Fair Value, Total	3,762	757
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	$ 7	$ 13