Fair Value of Assets and Liabilities - Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 27, 2020	Dec. 28, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash Equivalents	$ 148,409	$ 118,999
Investments in equity securities	12,899	12,969
Mutual funds	10,650	10,464
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash Equivalents	148,409	118,999
Investments in equity securities	12,899	12,969
Mutual funds	10,650	10,464
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash Equivalents	0	0
Investments in equity securities	0	0
Mutual funds	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash Equivalents	0	0
Investments in equity securities	0	0
Mutual funds	$ 0	$ 0