Fair Value Measurements - Financial Assets and Liabilities Measured and Recognized at Fair Value on a Recurring Basis (Details) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017
Money Market Funds
Assets:
Assets, Fair Value Measurements	$ 22,844	$ 20,950
Earn Out Liability
Liabilities:
Liabilities, Fair Value Measurements	364	572
Level 1 | Money Market Funds
Assets:
Assets, Fair Value Measurements	22,844	20,950
Level 3 | Earn Out Liability
Liabilities:
Liabilities, Fair Value Measurements	$ 364	$ 572