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Commitments and Contingencies - Changes to Net Insurance Liabilities (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Contingencies And Commitments [Line Items]
Beginning Balance	$ 393wm_NetInsuranceClaimsLiability	$ 367wm_NetInsuranceClaimsLiability	$ 350wm_NetInsuranceClaimsLiability
Self-insurance expense (benefit)	159wm_SelfInsuranceExpenseBenefit	172wm_SelfInsuranceExpenseBenefit	163wm_SelfInsuranceExpenseBenefit
Cash (paid) received	(138)wm_CashPaidReceived	(146)wm_CashPaidReceived	(146)wm_CashPaidReceived
Ending Balance	414wm_NetInsuranceClaimsLiability	393wm_NetInsuranceClaimsLiability	367wm_NetInsuranceClaimsLiability
Current portion at December 31, 2013	112wm_NetInsuranceClaimsLiabilityCurrent
Long-term portion at December 31, 2013	302wm_NetInsuranceClaimsLiabilityLongTerm
Gross Claims Liability [Member]
Contingencies And Commitments [Line Items]
Beginning Balance	590	569	511
Self-insurance expense (benefit)	168	177	222
Cash (paid) received	(161)	(156)	(164)
Ending Balance	597	590	569
Current portion at December 31, 2013	129
Long-term portion at December 31, 2013	468
Receivables Associated with Insured Claims [Member]
Contingencies And Commitments [Line Items]
Beginning Balance	(197)	(202)	(161)
Self-insurance expense (benefit)	(9)	(5)	(59)
Cash (paid) received	23	10	18
Ending Balance	(183)	(197)	(202)
Current portion at December 31, 2013	(17)
Long-term portion at December 31, 2013	$ (166)