INVESTMENTSThe amortized cost and fair value of short-term investments and available-for-sale fixed maturity securities at June 30, 2025 and December 31, 2024 are as follows:
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | June 30, 2025 | | Amortized Cost | | Allowance for Expected Credit Losses | | Gross Unrealized Gains | | Gross Unrealized Losses | | Fair Value | | (dollars in millions) | | Fixed maturities: | | | | | | | | | | U.S. Treasury securities | $ | 47.4 | | | $ | — | | | $ | 0.7 | | | $ | (0.1) | | | $ | 48.0 | | | Municipal securities | 22.3 | | | — | | | 0.2 | | | (0.2) | | | 22.3 | | | Corporate debt securities | 121.7 | | | — | | | 1.3 | | | (0.4) | | | 122.6 | | | Asset-backed securities | 125.5 | | | — | | | 1.1 | | | (0.3) | | | 126.3 | | | Total fixed maturities | 316.9 | | | — | | | 3.3 | | | (1.0) | | | 319.2 | | | Short-term investments | 3.5 | | | — | | | — | | | — | | | 3.5 | | | Total | $ | 320.4 | | | $ | — | | | $ | 3.3 | | | $ | (1.0) | | | $ | 322.7 | | | | | | | | | | | | | December 31, 2024 | | Amortized Cost | | Allowance for Expected Credit Losses | | Gross Unrealized Gains | | Gross Unrealized Losses | | Fair Value | | (dollars in millions) | | Fixed maturities: | | | | | | | | | | U.S. Treasury securities and agencies | $ | 46.5 | | | $ | — | | | $ | — | | | $ | (0.3) | | | $ | 46.2 | | | Municipal securities | 23.9 | | | — | | | 0.1 | | | (0.5) | | | 23.5 | | | Corporate debt securities | 106.6 | | | — | | | 0.3 | | | (1.2) | | | 105.7 | | | Asset-backed securities | 117.3 | | | — | | | 0.4 | | | (1.1) | | | 116.6 | | | Total fixed maturities | 294.3 | | — | | | 0.8 | | (3.1) | | 292.0 | | Short-term investments | 14.8 | | — | | | — | | | — | | | 14.8 | | Total | $ | 309.1 | | | $ | — | | | $ | 0.8 | | | $ | (3.1) | | | $ | 306.8 | | | | | | | | | | | |
Management reviewed the available-for-sale fixed maturity securities and short-term investments at each balance sheet date to consider whether it was necessary to recognize a credit loss as of June 30, 2025 and December 31, 2024. We do not intend to sell the securities and it is not more likely than not that we will be required to sell the securities before recovery. Management concluded that the unrealized losses on the available-for-sale fixed maturity securities and short-term investments were due to non-credit related factors and, therefore, there was no allowance for credit loss as of June 30, 2025 and December 31, 2024. The following tables reflect the gross unrealized losses and fair value of short-term investments and available-for-sale fixed maturity securities, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at June 30, 2025 and December 31, 2024: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | June 30, 2025 | | Less than 12 Months | | 12 Months or More | | Total | | Fair Value | | Unrealized
Loss | | Fair Value | | Unrealized
Loss | | Fair Value | | Unrealized
Loss | | (dollars in millions) | | Fixed maturities: | | | | | | | | | | | | U.S. Treasury securities | $ | 2.7 | | | $ | — | | | $ | 0.7 | | | $ | (0.1) | | | $ | 3.4 | | | $ | (0.1) | | | Municipal securities | 1.3 | | | — | | | 8.3 | | | (0.2) | | | 9.6 | | | (0.2) | | | Corporate debt securities | 26.1 | | | (0.1) | | | 11.2 | | | (0.3) | | | 37.3 | | | (0.4) | | | Asset-backed securities | 17.4 | | | (0.1) | | | 8.0 | | | (0.2) | | | 25.4 | | | (0.3) | | | Total fixed maturities | 47.5 | | | (0.2) | | | 28.2 | | | (0.8) | | | 75.7 | | | (1.0) | | | Short-term investments | 3.5 | | | — | | | — | | | — | | | 3.5 | | | — | | | Total | $ | 51.0 | | | $ | (0.2) | | | $ | 28.2 | | | $ | (0.8) | | | $ | 79.2 | | | $ | (1.0) | | | | | | | | | | | | | | | December 31, 2024 | | Less than 12 Months | | 12 Months or More | | Total | | Fair Value | | Unrealized
Loss | | Fair Value | | Unrealized
Loss | | Fair Value | | Unrealized
Loss | | (dollars in millions) | | Fixed maturities: | | | | | | | | | | | | U.S. Treasury securities and agencies | $ | 26.4 | | | $ | (0.3) | | | $ | 1.8 | | | $ | — | | | $ | 28.2 | | | $ | (0.3) | | | Municipal securities | 7.1 | | | (0.1) | | | 10.4 | | | (0.4) | | | 17.5 | | | (0.5) | | | Corporate debt securities | 49.5 | | | (0.6) | | | 21.1 | | | (0.6) | | | 70.6 | | | (1.2) | | | Asset backed securities | 53.6 | | | (0.6) | | | 10.6 | | | (0.5) | | | 64.2 | | | (1.1) | | | Total fixed maturities | 136.6 | | | (1.6) | | | 43.9 | | | (1.5) | | | 180.5 | | | (3.1) | | | Short-term investments | 6.4 | | | — | | | — | | | — | | | 6.4 | | | — | | | Total | $ | 143.0 | | | $ | (1.6) | | | $ | 43.9 | | | $ | (1.5) | | | $ | 186.9 | | | $ | (3.1) | |
Other Investments As of June 30, 2025 and December 31, 2024, other investments related to our private equity investments were $4.4 million. There were no realized or unrealized gains or losses or impairment losses recognized on private equity investments for the three and six months ended June 30, 2025 and 2024. There were no realized gains or losses on short-term investments and available-for-sale fixed maturities for the three and six months ended June 30, 2025 and 2024. The following table sets forth the amortized cost and fair value of short-term investments and available-for-sale fixed maturity securities by contractual maturity at June 30, 2025: | | | | | | | | | | | | | | | | | June 30, 2025 | | | | | | Amortized Cost | | Fair Value | | | | | | (dollars in millions) | | | | | | Due in one year or less | $ | 32.0 | | | $ | 31.9 | | | | | | | Due after one year through five years | 213.6 | | | 215.4 | | | | | | | Due five years through 10 years | 36.8 | | | 37.3 | | | | | | | Due after 10 years | 38.0 | | | 38.1 | | | | | | | Total | $ | 320.4 | | | $ | 322.7 | | | | | |
Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations with or without call or prepayment penalties. The following table sets forth the components of net investment income for the three and six months ended June 30, 2025 and 2024:
| | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended June 30, | | Six Months Ended June 30, | | 2025 | | 2024 | | 2025 | | 2024 | | (dollars in millions) | | Interest on fixed maturities and short-term investments | $ | 3.6 | | | $ | 2.3 | | | $ | 7.0 | | | $ | 4.0 | | | Interest on cash and cash equivalents | 6.3 | | | 8.2 | | | 12.3 | | | 16.3 | | | | | | | | | | | Total | 9.9 | | | 10.5 | | | 19.3 | | | 20.3 | | | Investment expense | (0.5) | | | (0.5) | | | (1.2) | | | (1.1) | | | Net investment income | $ | 9.4 | | | $ | 10.0 | | | $ | 18.1 | | | $ | 19.2 | |
The following tables summarize the credit ratings of short-term investments and available-for-sale fixed maturity securities at June 30, 2025 and December 31, 2024:
| | | | | | | | | | | | | | | | | | | June 30, 2025 | | Amortized Cost | | Fair Value | | % of Total
Fair Value | | (dollars in millions) | | S&P Global rating or equivalent | | | | | | | AAA | $ | 67.5 | | | $ | 67.8 | | | 21.0 | % | | AA+, AA, AA-, A-1+ | 151.5 | | | 152.7 | | | 47.3 | | | A+, A, A- | 82.0 | | | 82.6 | | | 25.6 | | | BBB+, BBB, BBB- | 19.3 | | | 19.5 | | | 6.1 | | | BB+ | 0.1 | | | 0.1 | | | — | | | Total | $ | 320.4 | | | $ | 322.7 | | | 100.0 | % |
| | | | | | | | | | | | | | | | | | | December 31, 2024 | | Amortized Cost | | Fair Value | | % of Total
Fair Value | | (dollars in millions) | | S&P Global rating or equivalent | | | | | | | AAA | $ | 75.2 | | | $ | 74.8 | | | 24.4 | % | | AA+, AA, AA-, A-1+ | 146.0 | | | 145.0 | | 47.3 | | | A+, A, A- | 67.8 | | | 67.1 | | 21.9 | | | BBB+, BBB, BBB- | 20.1 | | | 19.9 | | 6.4 | | | Total | $ | 309.1 | | | $ | 306.8 | | | 100.0 | % |
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