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INVESTMENTS - Schedule of Gross Realized Gains and Losses (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | $ 147.5 | $ 51.1
Less than 12 months, gross unrealized losses | (1.6) | (0.7)
12 months or longer, fair value | 59.8 | 102.5
12 months or longer, gross unrealized losses | (1.2) | (1.6)
Total Fair Value | 207.3 | 153.6
Total Gross Unrealized Losses | (2.7) | (2.2)
Short-term investments |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 0.0 |
Less than 12 months, gross unrealized losses | 0.0 |
12 months or longer, fair value | 6.0 |
12 months or longer, gross unrealized losses | (0.1) |
Total Fair Value | 6.0 |
Total Gross Unrealized Losses | (0.1) |
U.S Treasury |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 1.1 | 3.4
Less than 12 months, gross unrealized losses | 0.0 | (0.1)
12 months or longer, fair value | 1.4 | 5.0
12 months or longer, gross unrealized losses | 0.0 | (0.1)
Total Fair Value | 2.5 | 8.5
Total Gross Unrealized Losses | 0.0 | (0.1)
Municipal |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 3.4 | 6.4
Less than 12 months, gross unrealized losses | (0.1) | (0.1)
12 months or longer, fair value | 1.6 | 10.4
12 months or longer, gross unrealized losses | 0.0 | (0.1)
Total Fair Value | 4.9 | 16.8
Total Gross Unrealized Losses | (0.1) | (0.2)
Corporate |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 64.3 | 11.4
Less than 12 months, gross unrealized losses | (0.5) | (0.1)
12 months or longer, fair value | 26.6 | 48.0
12 months or longer, gross unrealized losses | (0.4) | (0.8)
Total Fair Value | 90.9 | 59.4
Total Gross Unrealized Losses | (0.9) | (0.9)
Mortgage and other asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 78.5 | 29.8
Less than 12 months, gross unrealized losses | (1.0) | (0.4)
12 months or longer, fair value | 26.4 | 33.1
12 months or longer, gross unrealized losses | (0.7) | (0.5)
Total Fair Value | 104.9 | 62.9
Total Gross Unrealized Losses | $ (1.7) | $ (0.9)

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