The effect of our derivative instruments in fair value and cash flow hedging relationships on the consolidated statements of income for the years ended December 31, 2023, 2022 and 2021 follows (in millions):


	Classification and Amount of (Loss) Gain Recognized in Income on Fair Value and Cash Flow Hedging Relationships
	2023		2022		2021
	Interest Expense		Interest Expense		Interest Expense

Total amounts of expense line items presented in the consolidated statements of income in which the effects of fair value or cash flow hedges are recorded	$	(508.2)	$	(395.6)	$	(314.6)

The effects of fair value and cash flow hedging relationships in Subtopic 815-20:
(Loss) gain on fair value hedging relationships:
Interest rate swaps:
Net swap settlements	$	(2.2)	$	2.9	$	7.9
Net periodic loss	$	(1.1)	$	(3.3)	$	(0.1)

(Loss) gain on cash flow hedging relationships:
Amount of (loss) gain reclassified from accumulated other comprehensive loss into earnings, net of tax
Interest rate swap locks	$	(3.8)	$	(4.4)	$	(4.6)
2022 Interest Rate Swap	$	13.1	$	3.3	$	—

The effects of derivative instruments not in Subtopic 815-20:
Gain (loss) on free-standing derivative instruments:
Interest rate swaps:
Gain (loss) on change in fair value of free-standing derivative instruments	$	1.0	$	(5.0)	$	(4.4)
Interest rate contract:
Net (loss) gain on change in fair value of free-standing derivative instruments	$	(1.9)	$	2.1	$	0.3

In measuring fair values of assets and liabilities, we use valuation techniques that maximize the use of observable inputs (Level 1) and minimize the use of unobservable inputs (Level 3). We also use market data or assumptions that we believe market participants would use in pricing an asset or liability, including assumptions about risk when appropriate.

As of December 31, 2023 and 2022, our assets and liabilities that are measured at fair value on a recurring basis include the following:


	December 31, 2023
			Fair Value
	Carrying Amount		Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market mutual funds - restricted cash and marketable securities and other assets	$	43.1	$	43.1	$	43.1	$	—	$	—
Bonds - restricted cash and marketable securities and other assets	76.3		76.3		—		76.3		—
Derivative and hedging assets - other assets, prepaid expenses and other current assets	78.3		78.3		—		78.3		—
Total assets	$	197.7	$	197.7	$	43.1	$	154.6	$	—
Liabilities:
Derivative and hedging liabilities - other accrued liabilities and other long-term liabilities	$	79.6	$	79.6	$	—	$	79.6	$	—

Contingent consideration - other accrued liabilities and other long-term liabilities	63.6		63.6		—		—		63.6
Total liabilities	$	143.2	$	143.2	$	—	$	79.6	$	63.6


	December 31, 2022
			Fair Value
	Carrying Amount		Total		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Money market mutual funds	$	38.3	$	38.3	$	38.3	$	—	$	—
Bonds - restricted cash and marketable securities and other assets	56.9		56.9		—		56.9		—
Derivative and hedging assets - other assets	105.8		105.8		—		105.8		—
Total assets	$	201.0	$	201.0	$	38.3	$	162.7	$	—
Liabilities:
Derivative and hedging liabilities - other accrued liabilities and other long-term liabilities	$	102.0	$	102.0	$	—	$	102.0	$	—
Contingent consideration - other accrued liabilities and other long-term liabilities	65.1		65.1		—		—		65.1
Total liabilities	$	167.1	$	167.1	$	—	$	102.0	$	65.1

As of December 31, 2023 and 2022, the carrying value of our total debt was $12.8 billion and $11.8 billion, respectively, and the fair value of our total debt was $12.5 billion and $11.1 billion, respectively. The estimated fair value of our fixed rate senior notes and debentures is based on quoted market prices. The fair value of our remaining notes payable, tax-exempt financings and borrowings under our credit facilities approximates the carrying value because the interest rates are variable. The fair value estimates -are based on Level 2 inputs of the fair value hierarchy as of December 31, 2023 and 2022. See Note 9, Debt, for further information related to our debt.

In 2015, we entered into a waste management contract with the County of Sonoma, California to operate the county's waste management facilities. As of December 31, 2023, the Sonoma contingent consideration represents the fair value of $58.8 million payable to the County of Sonoma based on the achievement of future annual tonnage targets through the expected

remaining capacity of the landfill. The potential undiscounted amount of all future contingent payments that we could be required to make under the waste management contract is estimated to be between approximately $81 million and $114 million. During 2023, the activity in the contingent consideration liability included accretion, which was offset by concession payments made in the ordinary course of business. There were no changes to the estimate of fair value.