Employee Benefit Plans - Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2022 |
Jan. 01, 2022 |
Jan. 02, 2021 |
|
| Pension Benefits | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 2.63% | 2.04% | 2.90% |
| Expected long-term rate of return on plan assets, net periodic benefit cost | 5.00% | 5.00% | 7.00% |
| Pension Benefits | Summit Materials, LLC | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 2.63% | 2.04% | 2.90% |
| Expected long-term rate of return on plan assets, net periodic benefit cost | 5.00% | 5.00% | 7.00% |
| Healthcare & Life Ins | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 2.31% | 1.82% | 2.79% |
| Healthcare & Life Ins | Summit Materials, LLC | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Discount rate | 2.31% | 1.82% | 2.79% |