Investment Securities (Tables)
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6 Months Ended |
Jun. 30, 2025 |
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| Investments, Debt and Equity Securities [Abstract] |
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| Amortized Cost and Approximate Fair Values of Investment Securities |
The amortized cost and the approximate fair values of investment securities are summarized as follows: | | | | | | | | | | | | | | | | | | June 30, 2025 | Amortized
Cost | | | Gross
Unrealized
Gains | Gross
Unrealized
Losses | Estimated
Fair
Value | | Available-for-Sale: | | | | | | | | U.S. Treasury notes | $ | 245.7 | | | | $ | — | | $ | (11.8) | | $ | 233.9 | | | State, county, and municipal securities | 249.2 | | | | — | | (35.8) | | 213.4 | | | Obligations of U.S. government agencies | 213.2 | | | | — | | (6.5) | | 206.7 | | | U.S. agency commercial mortgage-backed securities | 995.7 | | | | 1.0 | | (49.6) | | 947.1 | | | U.S. agency residential mortgage-backed securities | 1,198.2 | | | | 1.2 | | (88.0) | | 1,111.4 | | | U.S. agency collateralized mortgage obligations | 1,072.2 | | | | 1.4 | | (80.0) | | 993.6 | | | Private mortgage-backed securities | 205.5 | | | | — | | (23.2) | | 182.3 | | | Collateralized loan obligation | 625.8 | | | | 1.0 | | — | | 626.8 | | | Corporate securities | 239.0 | | | | — | | (12.0) | | 227.0 | | | | | | | | | | Total | $ | 5,044.5 | | | | $ | 4.6 | | $ | (306.9) | | $ | 4,742.2 | |
| | | | | | | | | | | | | | | | | | June 30, 2025 | Amortized Cost(1) | | | Gross
Unrealized
Gains | Gross
Unrealized
Losses | Estimated
Fair
Value | | Held-to-Maturity: | | | | | | | | U.S. Treasury notes | $ | 100.0 | | | | $ | — | | $ | (0.1) | | $ | 99.9 | | | State, county, and municipal securities | 175.8 | | | | 0.2 | | (23.5) | | 152.5 | | | Obligations of U.S. government agencies | 466.8 | | | | — | | (45.2) | | 421.6 | | | U.S. agency commercial mortgage-backed securities | 369.7 | | | | — | | (24.8) | | 344.9 | | | U.S. agency residential mortgage-backed securities | 1,013.4 | | | | 0.2 | | (105.1) | | 908.5 | | | U.S. agency collateralized mortgage obligations | 405.0 | | | | 0.5 | | (54.1) | | 351.4 | | | Corporate securities | 40.0 | | | | — | | (1.8) | | 38.2 | | | | | | | | | | Total | $ | 2,570.7 | | | | $ | 0.9 | | $ | (254.6) | | $ | 2,317.0 | | (1) Amortized cost presented above is net of an allowance for credit losses of $0.7 million and includes $6.9 million of unamortized gains and $14.8 million of unamortized losses related to the 2021 and 2022 transfer of securities from available-for-sale to held-to-maturity, respectively. |
| | | | | | | | | | | | | | | | | | December 31, 2024 | Amortized
Cost | | | Gross
Unrealized
Gains | Gross
Unrealized
Losses | Estimated
Fair
Value | | Available-for-Sale: | | | | | | | | U.S. Treasury notes | $ | 245.0 | | | | $ | — | | $ | (18.1) | | $ | 226.9 | | | State, county, and municipal securities | 252.0 | | | | — | | (40.0) | | 212.0 | | | Obligations of U.S. government agencies | 224.1 | | | | — | | (10.8) | | 213.3 | | | U.S. agency commercial mortgage-backed securities | 1,057.2 | | | | 0.1 | | (74.5) | | 982.8 | | | U.S. agency residential mortgage-backed securities | 1,301.2 | | | | 0.4 | | (125.8) | | 1,175.8 | | | U.S. agency collateralized mortgage obligations | 1,156.9 | | | | 0.6 | | (106.6) | | 1,050.9 | | | Private mortgage-backed securities | 218.1 | | | | — | | (27.6) | | 190.5 | | | Collateralized loan obligation | 770.7 | | | | 1.3 | | — | | 772.0 | | | Corporate securities | 249.6 | | | | — | | (16.7) | | 232.9 | | | | | | | | | | Total | $ | 5,474.8 | | | | $ | 2.4 | | $ | (420.1) | | $ | 5,057.1 | |
| | | | | | | | | | | | | | | | | | | December 31, 2024 | Amortized Cost(1) | | | Gross
Unrealized
Gains | Gross
Unrealized
Losses | Estimated
Fair
Value | | | Held-to-Maturity: | | | | | | | | | U.S. Treasury notes | $ | 99.8 | | | | $ | — | | $ | (0.4) | | $ | 99.4 | | | | State, county, and municipal securities | 176.3 | | | | 0.2 | | (26.7) | | 149.8 | | | | Obligations of U.S. government agencies | 470.1 | | | | — | | (59.9) | | 410.2 | | | | U.S. agency commercial mortgage-backed securities | 374.9 | | | | — | | (33.4) | | 341.5 | | | | U.S. agency residential mortgage-backed securities | 1,082.5 | | | | — | | (140.7) | | 941.8 | | | | U.S. agency collateralized mortgage obligations | 427.8 | | | | — | | (66.1) | | 361.7 | | | | Corporate securities | 57.0 | | | | — | | (2.8) | | 54.2 | | | | | | | | | | | | Total | $ | 2,688.4 | | | | $ | 0.2 | | $ | (330.0) | | $ | 2,358.6 | | | (1) Amortized cost presented above is net of an allowance for credit losses of $0.9 million and includes $8.0 million of unamortized gains and $15.9 million of unamortized losses related to the 2021 and 2022 transfer of securities from available-for-sale to held-to-maturity, respectively. | |
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| Maturities of Investment Securities |
| | | | | | | | | | | | | | | | | | | | Available-for-Sale | | Held-to-Maturity | | June 30, 2025 | Amortized
Cost | Estimated
Fair Value | | Amortized
Cost | Estimated
Fair Value | | Within one year | $ | 103.7 | | $ | 102.4 | | | $ | 108.1 | | $ | 108.0 | | | After one year but within five years | 1,296.0 | | 1,244.0 | | | 446.6 | | 427.8 | | | After five years but within ten years | 1,318.2 | | 1,247.7 | | | 442.0 | | 397.8 | | | After ten years | 2,326.6 | | 2,148.1 | | | 1,574.0 | | 1,383.4 | | | Total | $ | 5,044.5 | | $ | 4,742.2 | | | $ | 2,570.7 | | $ | 2,317.0 | |
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| Schedule of Unrealized Loss on Investments |
The following tables show the gross unrealized losses and fair values of available-for-sale investment securities and the length of time individual investment securities have been in an unrealized loss position as of June 30, 2025 and December 31, 2024. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Less than 12 Months | | 12 Months or More | | Total | | June 30, 2025 | Fair
Value | Gross
Unrealized
Losses | | Fair
Value | Gross
Unrealized
Losses | | Fair
Value | Gross
Unrealized
Losses | | Available-for-Sale: | | | | | | | | | | U.S. Treasury notes | $ | — | | $ | — | | | $ | 233.9 | | $ | (11.8) | | | $ | 233.9 | | $ | (11.8) | | | State, county, and municipal securities | — | | — | | | 211.6 | | (35.8) | | | 211.6 | | (35.8) | | | Obligations of U.S. government agencies | 1.0 | | — | | | 200.7 | | (6.5) | | | 201.7 | | (6.5) | | | U.S. agency commercial mortgage-backed securities | — | | — | | | 898.0 | | (49.6) | | | 898.0 | | (49.6) | | | U.S. agency residential mortgage-backed securities | 32.9 | | (0.6) | | | 1,022.3 | | (87.4) | | | 1,055.2 | | (88.0) | | | U.S. agency collateralized mortgage obligations | 6.8 | | — | | | 936.5 | | (80.0) | | | 943.3 | | (80.0) | | | Private mortgage-backed securities | — | | — | | | 182.2 | | (23.2) | | | 182.2 | | (23.2) | | | | | | | | | | | | Corporate securities | 13.0 | | — | | | 192.1 | | (12.0) | | | 205.1 | | (12.0) | | | | | | | | | | | | Total | $ | 53.7 | | $ | (0.6) | | | $ | 3,877.3 | | $ | (306.3) | | | $ | 3,931.0 | | $ | (306.9) | | | | | | | | | | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Less than 12 Months | | 12 Months or More | | Total | | December 31, 2024 | Fair
Value | Gross
Unrealized
Losses | | Fair
Value | Gross
Unrealized
Losses | | Fair
Value | Gross
Unrealized
Losses | | Available-for-Sale: | | | | | | | | | | U.S. Treasury notes | $ | — | | $ | — | | | $ | 226.8 | | $ | (18.1) | | | $ | 226.8 | | $ | (18.1) | | | State, county, and municipal securities | — | | — | | | 210.1 | | (40.0) | | | 210.1 | | (40.0) | | | Obligations of U.S. government agencies | 3.6 | | — | | | 206.2 | | (10.8) | | | 209.8 | | (10.8) | | | U.S. agency commercial mortgage-backed securities | 38.1 | | (0.4) | | | 934.9 | | (74.1) | | | 973.0 | | (74.5) | | | U.S. agency residential mortgage-backed securities | 33.7 | | (1.5) | | | 1,086.2 | | (124.3) | | | 1,119.9 | | (125.8) | | | U.S. agency collateralized mortgage obligations | 20.5 | | (0.3) | | | 987.1 | | (106.3) | | | 1,007.6 | | (106.6) | | | Private mortgage-backed securities | — | | — | | | 190.4 | | (27.6) | | | 190.4 | | (27.6) | | | Collateralized loan obligation | 10.0 | | — | | | — | | — | | | 10.0 | | — | | | Corporate securities | 27.5 | | (0.5) | | | 205.5 | | (16.2) | | | 233.0 | | (16.7) | | | | | | | | | | | | Total | $ | 133.4 | | $ | (2.7) | | | $ | 4,047.2 | | $ | (417.4) | | | $ | 4,180.6 | | $ | (420.1) | | | | | | | | | | |
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