Schedule of Unrealized Loss on Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Dec. 28, 2019	Dec. 29, 2018
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	$ 10,525	$ 45,960
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	47	354
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	4,260	43,423
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	3	863
Available-for-sale investments with unrealized losses, Fair Value, Total	14,785	89,383
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	50	1,217
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	571
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	1
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	0	620
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	0	4
Available-for-sale investments with unrealized losses, Fair Value, Total	571	620
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	1	4
Corporate bonds and direct obligations of government agencies
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	8,728	45,960
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	41	354
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value	4,260	42,803
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss	3	859
Available-for-sale investments with unrealized losses, Fair Value, Total	12,988	88,763
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	44	$ 1,213
U.S. Treasury obligations
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	1,226
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	5
Available-for-sale investments with unrealized losses, Fair Value, Total	1,226
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	$ 5