Summary of Significant Accounting Policies - Life Insurance Policies (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 26, 2020 USD ($) Individual	Jun. 26, 2020 USD ($) Individual	Dec. 31, 2019 USD ($)
Supplementary Information For Corporate Owned Life Insurance [Line Items]
Number of former employees covered under insurance policies | Individual	17	17
Average age of former employees covered under insurance policies		76 years
Gross cash surrender values of life insurance	$ 28,200	$ 28,200	$ 29,700
Loans on cash surrender value	26,000	26,000	27,200
Net cash surrender values of life insurance	2,989	2,989	3,133
Gross death benefit of life insurance contracts	37,100	37,100	37,700
Life insurance proceeds to be received upon the death of participants	10,800	10,800
Life insurance gain to be recognized upon death of participants	8,600	8,600
Non-taxable life insurance gain	389	389
Payments for Loans		1,900
Casualty Events [Member]
Supplementary Information For Corporate Owned Life Insurance [Line Items]
Non-taxable life insurance gain		400
Non-Qualified Defined Benefit Executive Supplemental Benefit Plan [Member]
Supplementary Information For Corporate Owned Life Insurance [Line Items]
Net cash surrender values of life insurance	$ 2,200	$ 2,200	$ 2,500