Fair Value Measurements (Summary of Valuation of Company's Financial Instruments by Various Levels) (Details) - USD ($) $ in Thousands	Jun. 28, 2020	Dec. 31, 2019
Assets:
Available-for-sale securities: U.S. treasuries	$ 20,030	$ 19,990
Fair value, measurements, recurring
Assets:
Cash equivalents: money-market funds	11,726	31,472
Available-for-sale securities: U.S. treasuries	20,030	19,990
Foreign currency forward contracts	0	27
Total assets measured at fair value	31,756	51,489
Liabilities:
Foreign currency forward contracts	27	375
Total liabilities measured at fair value	27	375
Fair value, measurements, recurring | Quoted market prices in active markets (Level 1)
Assets:
Cash equivalents: money-market funds	11,726	31,472
Available-for-sale securities: U.S. treasuries	20,030	19,990
Foreign currency forward contracts	0	0
Total assets measured at fair value	31,756	51,462
Liabilities:
Foreign currency forward contracts	0	0
Total liabilities measured at fair value	0	0
Fair value, measurements, recurring | Significant other observable inputs (Level 2)
Assets:
Cash equivalents: money-market funds	0	0
Available-for-sale securities: U.S. treasuries	0	0
Foreign currency forward contracts	0	27
Total assets measured at fair value	0	27
Liabilities:
Foreign currency forward contracts	27	375
Total liabilities measured at fair value	$ 27	$ 375