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Marketable Securities Held in Trusts (Tables)

6 Months Ended

Jun. 30, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of maturity dates for debt securities

The following table summarizes the balance by contractual maturity of the available-for-sale debt securities invested by the RCRA Trusts as of June 30, 2024. Actual maturities may differ from contractual maturities because the issuers of the securities may have the right to prepay obligations before the underlying contracts mature.

			June 30, 2024
Due in one year or less			$	19.7
Due after one year through five years			217.2
Due after five years through ten years			384.7
Due after ten years			57.3
Total debt securities			$	678.9

Schedule of Unrealized Loss on Investments

The following tables show gross unrealized losses and fair values of the RCRA Trusts’ available-for-sale securities that have been in a continuous unrealized loss position for which an allowance for credit losses has not been recorded as of June 30, 2024 and December 31, 2023:

			June 30, 2024												December 31, 2023
(in millions)			Fair Value						Gross Unrealized Losses						Fair Value						Gross Unrealized Losses
Securities that have been in a continuous loss position for less than 12 months:
Corporate debt securities			$	34.3					$	(0.3)					$	5.4					$	(0.1)
Municipal bonds			86.5						(1.1)						42.3						(0.2)
U.S. government bonds			265.2						(3.0)						26.4						(0.3)
			$	386.0					$	(4.4)					$	74.1					$	(0.6)
Securities that have been in a continuous loss position for more than 12 months:
Corporate debt securities			$	99.4					$	(8.0)					$	121.5					$	(8.3)
Municipal bonds			73.2						(3.3)						84.1						(3.9)
			$	172.6					$	(11.3)					$	205.6					$	(12.2)

Unrealized Gain (Loss) on Investments

The estimated fair value of the investments in the RCRA Trusts as of June 30, 2024 and December 31, 2023 are as follows:

			June 30, 2024
			Amortized Cost						Gross Unrealized Gains						Gross Unrealized Losses						Fair Value
Level 1
Cash and cash equivalents			$	2.3					$	—					$	—					$	2.3
Level 2
Corporate debt securities			199.2						0.6						(8.3)						191.5
Municipal bonds			208.5						0.8						(4.4)						204.9
U.S. government bonds			285.4						0.1						(3.0)						282.5
Total			$	695.4					$	1.5					$	(15.7)					$	681.2
			December 31, 2023
			Amortized Cost						Gross Unrealized Gains						Gross Unrealized Losses						Fair Value
Level 1
Cash and cash equivalents			$	1.0					$	—					$	—					$	1.0
Level 2
Corporate debt securities			204.6						1.9						(8.4)						198.1
Municipal bonds			206.9						1.9						(4.1)						204.7
U.S. government bonds			268.6						11.5						(0.3)						279.8
Total			$	681.1					$	15.3					$	(12.8)					$	683.6

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Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments.

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For all investments in an unrealized loss position, including those for which other-than-temporary impairments have not been recognized in earnings (including investments for which a portion of an other-than-temporary impairment has been recognized in other comprehensive income), a tabular disclosure of the aggregate related fair value of investments with unrealized losses and the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value).

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Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-6

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