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BUSINESS COMBINATIONS - Narrative (Details) - business | 3 Months Ended
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Mar. 31, 2021 | Mar. 31, 2020
Business Acquisition [Line Items] |  |
Number of businesses acquired |  | 2
Minimum |  |
Business Acquisition [Line Items] |  |
Useful life of finite lived intangible assets | 5 years |
Maximum |  |
Business Acquisition [Line Items] |  |
Useful life of finite lived intangible assets | 10 years |
Western | Tuck-in Solid Waste Collection Business |  |
Business Acquisition [Line Items] |  |
Number of businesses acquired | 1 | 1
Western | Recycling Operation |  |
Business Acquisition [Line Items] |  |
Number of businesses acquired | 1 |
Resource Solutions | Recycling Operation |  |
Business Acquisition [Line Items] |  |
Number of businesses acquired |  | 1

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