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Acquisitions and Divestitures - Pro Forma (Detail) - Advanced Disposal [Member] - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Operating revenues	$ 16,192	$ 16,660
Net income attributable to Waste Management, Inc.	$ 1,685	$ 1,472
Basic earnings per common share	$ 3.99	$ 3.47
Diluted earnings per common share	$ 3.96	$ 3.44
Basic (in shares)	423	425
Diluted (in shares)	425	428

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