Fair Value Measurements (Assets) (Details) - USD ($) $ in Thousands	Mar. 28, 2020	Dec. 28, 2019
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	$ 35,413	$ 52,073
Fair value, measurements, recurring
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	35,413	52,073
Derivative financial instruments - liability	2,504
Derivative financial instruments - asset		276
Deferred stock-based compensation	5,065	7,503
Fair value, measurements, recurring | Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	35,413	52,073
Derivative financial instruments - liability	0
Derivative financial instruments - asset		0
Deferred stock-based compensation	0	0
Fair value, measurements, recurring | Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	0	0
Derivative financial instruments - liability	2,504
Derivative financial instruments - asset		276
Deferred stock-based compensation	5,065	7,503
Fair value, measurements, recurring | Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents (including money market funds)	0	0
Derivative financial instruments - liability	0
Derivative financial instruments - asset		0
Deferred stock-based compensation	0	0
Fair value, measurements, recurring | Government securities
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	6,797	6,339
Fair value, measurements, recurring | Government securities | Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Fair value, measurements, recurring | Government securities | Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	6,797	6,339
Fair value, measurements, recurring | Government securities | Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Fair value, measurements, recurring | Corporate Bonds
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	6,395	6,323
Fair value, measurements, recurring | Corporate Bonds | Quoted prices in active markets for identical assets (Level 1)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Fair value, measurements, recurring | Corporate Bonds | Significant other observable inputs (Level 2)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	6,395	6,323
Fair value, measurements, recurring | Corporate Bonds | Significant unobservable inputs (Level 3)
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	$ 0	$ 0