Significant Accounting Policies - Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 28, 2021	Dec. 27, 2020
Carrying Value
Measurement of financial assets and liabilities at fair value on a recurring basis
Cash surrender value of life insurance policies	$ 38,721	$ 37,578
Interest rate swap liabilities	11,615	13,452
Measured on Recurring Basis | Level 1
Measurement of financial assets and liabilities at fair value on a recurring basis
Cash surrender value of life insurance policies	38,721	37,578
Measured on Recurring Basis | Level 2
Measurement of financial assets and liabilities at fair value on a recurring basis
Interest rate swap liabilities	$ 11,615	$ 13,452