Schedule of Unrealized Loss on Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Mar. 28, 2020	Dec. 28, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	$ 49,871	$ 10,525
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	1,758	47
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value		4,260
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss		3
Available-for-sale investments with unrealized losses, Fair Value, Total	49,871	14,785
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	1,758	50
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale investments with unrealized losses, Less than 12 months, Fair Value	523	571
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	48	1
Available-for-sale investments with unrealized losses, Fair Value, Total	523	571
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	48	1
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	49,348	8,728
Available-for-sale investments with unrealized losses, Less than 12 months, Unrealized Loss	1,710	41
Available-for-sale investments with unrealized losses, 12 months or longer, Fair Value		4,260
Available-for-sale investments with unrealized losses, 12 months or longer, Unrealized Loss		3
Available-for-sale investments with unrealized losses, Fair Value, Total	49,348	12,988
Available-for-sale investments with unrealized losses, Unrealized Loss, Total	$ 1,710	44
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