Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Mar. 30, 2019	Dec. 29, 2018
Assets
Total assets	$ 16,926	$ 60,845
Money market funds
Assets
Total assets	904	10,347
Corporate bonds
Assets
Total assets	16,022	23,512
U.S. agency notes
Assets
Total assets	0	2,999
U.S. treasuries
Assets
Total assets	0	23,987
Level 1
Assets
Total assets	904	34,334
Level 1 | Money market funds
Assets
Total assets	904	10,347
Level 1 | Corporate bonds
Assets
Total assets	0	0
Level 1 | U.S. agency notes
Assets
Total assets	0	0
Level 1 | U.S. treasuries
Assets
Total assets	0	23,987
Level 2
Assets
Total assets	16,022	26,511
Level 2 | Money market funds
Assets
Total assets	0	0
Level 2 | Corporate bonds
Assets
Total assets	16,022	23,512
Level 2 | U.S. agency notes
Assets
Total assets	0	2,999
Level 2 | U.S. treasuries
Assets
Total assets	0	0
Foreign currency exchange forward contracts
Liabilities
Foreign currency exchange forward contracts	(30)	(91)
Foreign currency exchange forward contracts | Level 1
Liabilities
Foreign currency exchange forward contracts	0	0
Foreign currency exchange forward contracts | Level 2
Liabilities
Foreign currency exchange forward contracts	$ (30)	$ (91)