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INCOME TAXES - Components of Deferred Income Tax Assets and Liabilities (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Deferred income tax assets and liabilities    
Balance at the beginning $ 582.6  
Balance at the end 534.0 $ 582.6
Non-capital loss carry forwards    
Deferred income tax assets and liabilities    
Balance at the beginning 464.7 446.8
Discontinued operations   (13.8)
Acquisitions via business combinations   5.7
Foreign exchange (2.7) 11.0
Recognized in net loss (5.7) 15.0
Balance at the end 456.3 464.7
Landfill closures and post-closure obligations    
Deferred income tax assets and liabilities    
Balance at the beginning 205.0 178.1
Acquisitions via business combinations   0.9
Foreign exchange (4.1) 9.8
Recognized in net loss 13.8 16.2
Balance at the end 214.7 205.0
Accrued liabilities    
Deferred income tax assets and liabilities    
Balance at the beginning 3.4 1.2
Acquisitions via business combinations   (0.3)
Foreign exchange (0.1) 1.2
Recognized in net loss 1.0 1.3
Balance at the end 4.3 3.4
Other    
Deferred income tax assets and liabilities    
Balance at the beginning 194.7 134.2
Discontinued operations   19.2
Acquisitions via business combinations 11.9 6.1
Foreign exchange (1.0) (2.0)
Recognized in net loss (23.0) 37.2
Recognized in other comprehensive loss (0.4)  
Balance at the end 182.2 194.7
Deferred income tax assets    
Deferred income tax assets and liabilities    
Balance at the beginning 867.8 760.3
Discontinued operations   5.4
Acquisitions via business combinations 11.9 12.4
Foreign exchange (7.9) 20.0
Recognized in net loss (13.9) 69.7
Recognized in other comprehensive loss (0.4)  
Balance at the end 857.5 867.8
Property and equipment    
Deferred income tax assets and liabilities    
Balance at the beginning 929.9 774.9
Discontinued operations   (13.5)
Acquisitions via business combinations 11.8 62.6
Foreign exchange (16.9) 60.0
Recognized in net loss (85.8) 45.9
Balance at the end 839.0 929.9
Intangible assets    
Deferred income tax assets and liabilities    
Balance at the beginning 592.1 711.7
Discontinued operations   (1.9)
Acquisitions via business combinations 85.0 3.4
Foreign exchange (4.5) (1.7)
Recognized in net loss (136.6) (119.4)
Balance at the end 536.0 592.1
Cash flow hedges    
Deferred income tax assets and liabilities    
Balance at the beginning (15.8) 5.8
Recognized in net loss 0.4  
Recognized in other comprehensive loss 9.8 (21.6)
Balance at the end (5.6) (15.8)
Other    
Deferred income tax assets and liabilities    
Balance at the beginning (55.8) (8.2)
Discontinued operations   (3.7)
Acquisitions via business combinations 3.3 (2.0)
Foreign exchange (1.2) (4.6)
Recognized in net loss 11.0 (37.3)
Balance at the end (42.7) (55.8)
Deferred income tax liabilities    
Deferred income tax assets and liabilities    
Balance at the beginning 1,450.4 1,484.2
Discontinued operations   (19.1)
Acquisitions via business combinations 100.1 64.0
Foreign exchange (22.6) 53.7
Recognized in net loss (211.0) (110.8)
Recognized in other comprehensive loss 9.8 (21.6)
Balance at the end $ 1,326.7 $ 1,450.4