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Landfill and Environmental Costs (Tables)
 3 Months Ended
Mar. 31, 2024
Environmental Remediation Obligations [Abstract]  
Schedule of accrued landfill and environmental costs
A summary of accrued landfill and environmental liabilities as of March 31, 2024 and December 31, 2023 follows:
20242023
Landfill final capping, closure and post-closure liabilities$1,967.9 $1,937.2 
Environmental remediation479.8 485.4 
Total accrued landfill and environmental costs2,447.7 2,422.6 
Less: current portion(141.2)(141.6)
Long-term portion$2,306.5 $2,281.0 
Schedule of final capping, closure and post-closure costs
The following table summarizes the activity in our asset retirement obligation liabilities, which includes liabilities for final capping, closure and post-closure, for the three months ended March 31, 2024 and 2023:
20242023
Asset retirement obligation liabilities, beginning of year$1,937.2 $1,786.4 
Non-cash additions14.3 15.0 
Asset retirement obligation adjustments(1.3)(8.4)
Payments(8.9)(8.8)
Accretion expense26.6 24.1 
Asset retirement obligation liabilities, end of period1,967.9 1,808.3 
Less: current portion(72.4)(73.9)
Long-term portion$1,895.5 $1,734.4 
Summary of activity in environmental remediation liabilities
The following table summarizes the activity in our environmental remediation liabilities for the three months ended March 31, 2024 and 2023:
20242023
Environmental remediation liabilities, beginning of year$485.4 $487.5 
Payments(9.8)(11.6)
Accretion expense (non-cash interest expense)4.2 4.6 
Environmental remediation liabilities, end of period479.8 480.5 
Less: current portion(68.8)(61.3)
Long-term portion$411.0 $419.2