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Assets and Liabilities Measured at Fair Value - Schedule of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financial assets
Fuel derivative	$ 0.2	$ 0.2
Deferred compensation plan assets	15.2	14.9
Financial liabilities
Fair value, net asset (liability)	(10.4)	(11.2)
Deferred compensation plan liabilities
Financial liabilities
Deferred compensation plan liabilities	(25.8)	(26.3)
Level 1
Financial assets
Fuel derivative	0.0	0.0
Deferred compensation plan assets	15.2	14.9
Financial liabilities
Fair value, net asset (liability)	(10.6)	(11.4)
Level 1 | Deferred compensation plan liabilities
Financial liabilities
Deferred compensation plan liabilities	(25.8)	(26.3)
Level 2
Financial assets
Fuel derivative	0.0	0.0
Deferred compensation plan assets	0.0	0.0
Financial liabilities
Fair value, net asset (liability)	0.0	0.0
Level 2 | Deferred compensation plan liabilities
Financial liabilities
Deferred compensation plan liabilities	0.0	0.0
Level 3
Financial assets
Fuel derivative	0.2	0.2
Deferred compensation plan assets	0.0	0.0
Financial liabilities
Fair value, net asset (liability)	0.2	0.2
Level 3 | Deferred compensation plan liabilities
Financial liabilities
Deferred compensation plan liabilities	$ 0.0	$ 0.0

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

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- Definition

Fair value of asset after deduction of liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

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