Fair Values of Financial Assets and Liabilities (Details) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Mar. 30, 2018	Dec. 31, 2017
Assets
Cash equivalents	$ 2,725	$ 2,665
Assets, fair value	2,752	2,815
Liabilities
Liabilities, fair value	1,484	4,104
Prepaid Expenses and Other Current Assets
Assets
Foreign currency forward contracts	27	150
Other Liabilities
Liabilities
Contingent consideration - Long-term	1,304	1,304
Accrued Expenses And Other Current Liabilities
Liabilities
Foreign currency forward contracts	180
Contingent consideration - Current		2,800
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash equivalents	2,725	2,665
Assets, fair value	2,725	2,665
Significant Other Observable Inputs (Level 2)
Assets
Assets, fair value	27	150
Liabilities
Liabilities, fair value	180
Significant Other Observable Inputs (Level 2) | Prepaid Expenses and Other Current Assets
Assets
Foreign currency forward contracts	27	150
Significant Other Observable Inputs (Level 2) | Accrued Expenses And Other Current Liabilities
Liabilities
Foreign currency forward contracts	180
Significant Other Unobservable Inputs (Level 3)
Liabilities
Liabilities, fair value	1,304	4,104
Significant Other Unobservable Inputs (Level 3) | Other Liabilities
Liabilities
Contingent consideration - Long-term	$ 1,304	1,304
Significant Other Unobservable Inputs (Level 3) | Accrued Expenses And Other Current Liabilities
Liabilities
Contingent consideration - Current		$ 2,800