Employee Benefit Plans - Amounts Recognized in Other Comprehensive (Gain) Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Pension Benefits
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	$ 1,728	$ 1,760	$ (1,300)
Amortization of prior year service cost	0	0	0
Amortization of gain	(326)	(202)	(312)
Total amount recognized	1,402	1,558	(1,612)
Pension Benefits \| Summit Materials, LLC
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	1,728	1,760	(1,300)
Amortization of prior year service cost	0	0	0
Amortization of gain	(326)	(202)	(312)
Total amount recognized	1,402	1,558	(1,612)
Healthcare & Life Ins
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	675	165	(172)
Amortization of prior year service cost	241	241	241
Amortization of gain	(89)	(39)	(118)
Total amount recognized	827	367	(49)
Healthcare & Life Ins \| Summit Materials, LLC
Amounts recognized in other comprehensive (income) loss:
Net actuarial loss (gain)	675	165	(172)
Amortization of prior year service cost	241	241	241
Amortization of gain	(89)	(39)	(118)
Total amount recognized	$ 827	$ 367	$ (49)

Amount after tax of reclassification adjustment from accumulated other comprehensive (income) loss other than net prior service cost (credit) related to pension and other postretirement benefit plans.

No definition available.

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- References

No definition available.

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- Definition

Amount, after tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

+ References

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-Publisher FASB
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- Definition

Amount, after tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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- Definition

Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

+ References

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