FAIR VALUE MEASUREMENTS - Fair Value of Other Temporary Investments and Cash (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 4,309.3	$ 4,395.1
Total Other Temporary Investments and Restricted Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost	224.3	236.9
Gross Unrealized Gains	21.6	26.9
Gross Unrealized Losses	(3.9)	(5.3)
Fair Value	242.0	258.5
Restricted Cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost	35.2	43.1
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Fair Value	35.2	43.1
Other Cash Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost	13.9	13.9
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Fair Value	13.9	13.9
Fixed Income Securities – Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost	164.2	167.2
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(3.9)	(5.3)
Fair Value	160.3	161.9
Equity Securities – Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost	11.0	12.7
Gross Unrealized Gains	21.6	26.9
Gross Unrealized Losses	0.0	0.0
Fair Value	$ 32.6	$ 39.6

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
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-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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