v3.22.4
Employee Benefit Plans - Obligations and Funded Status (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2022
Jan. 01, 2022
Jan. 02, 2021
Change in fair value of plan assets:      
Beginning of period $ 20,004    
End of period 17,043 $ 20,004  
Summit Materials, LLC      
Change in fair value of plan assets:      
Beginning of period 20,004    
End of period 17,043 20,004  
Pension Benefits      
Change in benefit obligations:      
Beginning of period 25,266 27,827  
Service cost 68 58 $ 71
Interest cost 640 550 733
Actuarial (gain) loss (5,360) (1,594)  
Change in plan provision 0 0  
Benefits paid (1,577) (1,575)  
End of period 19,037 25,266 27,827
Change in fair value of plan assets:      
Beginning of period 20,004 19,058  
Actual return on plan assets (1,606) 1,304  
Employer contributions 222 1,217  
Benefits paid (1,577) (1,575)  
End of period 17,043 20,004 19,058
Funded status of plans (1,994) (5,262)  
Current liabilities 0 0  
Noncurrent liabilities (1,994) (5,262)  
Liability recognized (1,994) (5,262)  
Amounts recognized in accumulated other comprehensive income:      
Net actuarial loss 5,170 8,261  
Prior service cost 0 0  
Total amount recognized 5,170 8,261  
Pension Benefits | Summit Materials, LLC      
Change in benefit obligations:      
Beginning of period 25,266 27,827  
Service cost 68 58 71
Interest cost 640 550 733
Actuarial (gain) loss (5,360) (1,594)  
Change in plan provision 0 0  
Benefits paid (1,577) (1,575)  
End of period 19,037 25,266 27,827
Change in fair value of plan assets:      
Beginning of period 20,004 19,058  
Actual return on plan assets (1,606) 1,304  
Employer contributions 222 1,217  
Benefits paid (1,577) (1,575)  
End of period 17,043 20,004 19,058
Funded status of plans (1,994) (5,262)  
Current liabilities 0 0  
Noncurrent liabilities (1,994) (5,262)  
Liability recognized (1,994) (5,262)  
Amounts recognized in accumulated other comprehensive income:      
Net actuarial loss 5,170 8,261  
Prior service cost 0 0  
Total amount recognized 5,170 8,261  
Healthcare & Life Ins      
Change in benefit obligations:      
Beginning of period 9,790 9,229  
Service cost 35 194 176
Interest cost 239 189 242
Actuarial (gain) loss (1,454) 1,143  
Change in plan provision (2,014) 0  
Benefits paid (1,025) (965)  
End of period 5,571 9,790 9,229
Change in fair value of plan assets:      
Beginning of period 0 0  
Actual return on plan assets 0 0  
Employer contributions 1,025 965  
Benefits paid (1,025) (965)  
End of period 0 0 0
Funded status of plans (5,571) (9,790)  
Current liabilities (484) (723)  
Noncurrent liabilities (5,087) (9,067)  
Liability recognized (5,571) (9,790)  
Amounts recognized in accumulated other comprehensive income:      
Net actuarial loss 1,919 3,591  
Prior service cost (3,167) (1,449)  
Total amount recognized (1,248) 2,142  
Healthcare & Life Ins | Summit Materials, LLC      
Change in benefit obligations:      
Beginning of period 9,790 9,229  
Service cost 35 194 176
Interest cost 239 189 242
Actuarial (gain) loss (1,454) 1,143  
Change in plan provision (2,014) 0  
Benefits paid (1,025) (965)  
End of period 5,571 9,790 9,229
Change in fair value of plan assets:      
Beginning of period 0 0  
Actual return on plan assets 0 0  
Employer contributions 1,025 965  
Benefits paid (1,025) (965)  
End of period 0 0 $ 0
Funded status of plans (5,571) (9,790)  
Current liabilities (484) (723)  
Noncurrent liabilities (5,087) (9,067)  
Liability recognized (5,571) (9,790)  
Amounts recognized in accumulated other comprehensive income:      
Net actuarial loss 1,919 3,591  
Prior service cost (3,167) (1,449)  
Total amount recognized $ (1,248) $ 2,142