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Employee Benefit Plans - Fair Value of Company's Pension Plans' Assets (Detail) - USD ($)
$ in Thousands
Dec. 30, 2017
Dec. 31, 2016
Jan. 02, 2016
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value $ 19,012 $ 18,395  
Intermediate - Government      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,620 1,770  
Intermediate - Corporate      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,872 2,658  
Short Term - Government      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 497 912  
Short Term - Corporate      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,702 3,613  
U.S. Large Cap Value      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,765 1,181  
U.S. Large Cap Growth      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 588 1,103  
U.S. Mid Cap Value      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 577  
U.S. Mid Cap Growth      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 546  
U.S. Small Cap Value      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 571 551  
U.S. Small Cap Growth      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 580 540  
Managed Futures      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 392 366  
International      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,547 1,099  
Emerging Markets      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   359  
Commodities Broad Basket      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 801 707  
Cash      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,522 2,094  
Precious Metals      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 383 319  
Pension Benefits      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 19,012 18,395 $ 18,336
Pension Benefits | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 19,012 18,395 $ 18,336
Pension Benefits | Intermediate - Government | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,620 1,770  
Pension Benefits | Intermediate - Corporate | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,872 2,658  
Pension Benefits | Short Term - Government | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 497 912  
Pension Benefits | Short Term - Corporate | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,702 3,613  
Pension Benefits | U.S. Large Cap Value | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,765 1,181  
Pension Benefits | U.S. Large Cap Growth | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 588 1,103  
Pension Benefits | U.S. Mid Cap Value | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 577  
Pension Benefits | U.S. Mid Cap Growth | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 546  
Pension Benefits | U.S. Small Cap Value | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 571 551  
Pension Benefits | U.S. Small Cap Growth | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 580 540  
Pension Benefits | Managed Futures | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 392 366  
Pension Benefits | International | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,547 1,099  
Pension Benefits | Emerging Markets | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   359  
Pension Benefits | Commodities Broad Basket | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 801 707  
Pension Benefits | Cash | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,522 2,094  
Pension Benefits | Precious Metals | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 383 319  
Quoted Prices in Active Markets for Identical Assets (Level 1)      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 9,301 9,442  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Intermediate - Government      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,068    
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short Term - Government      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 497    
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Large Cap Value      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,765 1,181  
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Large Cap Growth      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 588 1,103  
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Mid Cap Value      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 577  
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Mid Cap Growth      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 546  
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Small Cap Value      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 571 551  
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Small Cap Growth      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 580 540  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Managed Futures      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   366  
Quoted Prices in Active Markets for Identical Assets (Level 1) | International      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 677 1,099  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Emerging Markets      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   359  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commodities Broad Basket      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   707  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   2,094  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Precious Metals      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 383 319  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 9,301 9,442  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Intermediate - Government | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,068    
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Short Term - Government | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 497    
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | U.S. Large Cap Value | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,765 1,181  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | U.S. Large Cap Growth | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 588 1,103  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | U.S. Mid Cap Value | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 577  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | U.S. Mid Cap Growth | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 586 546  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | U.S. Small Cap Value | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 571 551  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | U.S. Small Cap Growth | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 580 540  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Managed Futures | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   366  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | International | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 677 1,099  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Emerging Markets | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   359  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Commodities Broad Basket | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   707  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Cash | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   2,094  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pension Benefits | Precious Metals | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 383 319  
Level 2      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 9,711 8,953  
Level 2 | Intermediate - Government      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 552 1,770  
Level 2 | Intermediate - Corporate      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,872 2,658  
Level 2 | Short Term - Government      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   912  
Level 2 | Short Term - Corporate      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,702 3,613  
Level 2 | Managed Futures      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 392    
Level 2 | International      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 870    
Level 2 | Commodities Broad Basket      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 801    
Level 2 | Cash      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,522    
Level 2 | Pension Benefits | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 9,711 8,953  
Level 2 | Pension Benefits | Intermediate - Government | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 552 1,770  
Level 2 | Pension Benefits | Intermediate - Corporate | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 3,872 2,658  
Level 2 | Pension Benefits | Short Term - Government | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value   912  
Level 2 | Pension Benefits | Short Term - Corporate | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 1,702 $ 3,613  
Level 2 | Pension Benefits | Managed Futures | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 392    
Level 2 | Pension Benefits | International | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 870    
Level 2 | Pension Benefits | Commodities Broad Basket | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value 801    
Level 2 | Pension Benefits | Cash | Summit Materials, LLC      
Pension Plans, Postretirement and Other Employee Benefits [Line Items]      
Total fair value $ 1,522