Fair Value Measurements - Assets (Details) - USD ($) $ in Thousands	Sep. 26, 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)	$ 109,385	$ 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)	109,385	52,073
Available-for-sale debt securities	13,200	12,500
Derivative financial instruments - liability	2,583
Derivative financial instruments - asset		276
Deferred stock-based compensation	6,480	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)	109,385	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	2,583
Derivative financial instruments - asset		276
Deferred stock-based compensation	6,480	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	6,696	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	6,696	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	6,984	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	6,984	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