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Investments - Aging of Gross Unrealized Losses (Details) - USD ($) $ in Millions | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Fair Value |  |
Less than 12 Months | $ 106.4 | $ 182.8
12 Months or More | 43.7 | 53.0
Fair Value | 150.1 | 235.8
Gross Unrealized Losses |  |
Less than 12 Months | (0.3) | (0.8)
12 Months or More | (0.3) | (0.5)
Gross Unrealized Losses | (0.6) | (1.3)
Corporate debt securities |  |
Fair Value |  |
Less than 12 Months | 85.0 | 149.4
12 Months or More | 43.7 | 53.0
Fair Value | 128.7 | 202.4
Gross Unrealized Losses |  |
Less than 12 Months | (0.2) | (0.6)
12 Months or More | (0.3) | (0.5)
Gross Unrealized Losses | (0.5) | (1.1)
U.S. Government obligations |  |
Fair Value |  |
Less than 12 Months | 12.1 | 27.6
12 Months or More | 0.0 | 0.0
Fair Value | 12.1 | 27.6
Gross Unrealized Losses |  |
Less than 12 Months | (0.1) | (0.2)
12 Months or More | 0.0 | 0.0
Gross Unrealized Losses | (0.1) | (0.2)
Asset-backed securities |  |
Fair Value |  |
Less than 12 Months | 9.3 | 5.8
12 Months or More | 0.0 | 0.0
Fair Value | 9.3 | 5.8
Gross Unrealized Losses |  |
Less than 12 Months | 0.0 | 0.0
12 Months or More | 0.0 | 0.0
Gross Unrealized Losses | 0.0 | 0.0
Non-U.S. government obligations |  |
Fair Value |  |
Less than 12 Months | 0.0 | 0.0
12 Months or More | 0.0 | 0.0
Fair Value | 0.0 | 0.0
Gross Unrealized Losses |  |
Less than 12 Months | 0.0 | 0.0
12 Months or More | 0.0 | 0.0
Gross Unrealized Losses | $ 0.0 | $ 0.0

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