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Benefit Plans - Additional Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 26, 2021
Sep. 27, 2020
Sep. 26, 2021
Sep. 27, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined contribution pension plan              
Benefit costs $ 24 $ 24 $ 60 $ 72 $ 94 $ 141 $ 24
Defined benefit plan assets contribution by employer 300 294 417 477      
401(k) [Member]              
Defined contribution pension plan              
Defined contribution plan employer discretionary contribution amount $ 1,019 $ 757 $ 2,020 $ 1,558      
Pension Plan [Member]              
Defined contribution pension plan              
Accumulated benefit obligation         6,551 5,993  
Benefit costs         94 141 24
Defined benefit plan assets contribution by employer         589 285 0
Defined benefit plan assets contribution by plan participant         0 $ 0 $ 0
Defined benefit plan expected future employer contributions next fiscal year         $ 367    
Section Four Hundred And One K Plan [Member]              
Defined contribution pension plan              
Defined contribution plan employer matching contribution percent of match         3.50% 3.50% 3.50%
Defined contribution plan employer discretionary contribution amount         $ 1,997 $ 1,141 $ 274
Section Four Hundred And One K Plan [Member] | Before Second Quarter Of Two Thousand And Twenty One [Member]              
Defined contribution pension plan              
Defined contribution plan employer discertionary contribution additional contribution accrued         $ 440