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Securities - Amortized Cost, Fair Value and Allowance for Credit Loss on Securities Held-to-Maturity (Details) - USD ($) $ in Thousands | Mar. 31, 2026 | Dec. 31, 2025 | Jun. 30, 2025 | Mar. 31, 2025 | Dec. 31, 2024 | Jun. 30, 2024
--- | --- | --- | --- | --- | --- | ---
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | $ 814,864 |  | $ 776,695 |  |  |
Unrealized gains |  | 11,724 |  | 10,381 |  |  |
Unrealized losses |  | 41,510 |  | 48,942 |  |  |
Fair value |  | 785,078 |  | 738,134 |  |  |
Allowance |  | 550 | $ 616 | 548 | $ 422 | $ 439 | $ 483
Net carrying value |  | 814,314 |  | 776,147 |  |  |
Accrued interest receivable |  | 7,000 |  | 4,900 |  |  |
U.S. Treasury Securities [Member] |  |  |  |  |  |  |
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | 13,890 |  | 15,850 |  |  |
Unrealized gains |  | 0 |  | 0 |  |  |
Unrealized losses |  | 633 |  | 868 |  |  |
Fair value |  | 13,257 |  | 14,982 |  |  |
Allowance |  | 0 |  | 0 |  |  |
Net carrying value |  | 13,890 |  | 15,850 |  |  |
State and Political Subdivisions [Member] |  |  |  |  |  |  |
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | 479,636 |  | 460,959 |  |  |
Unrealized gains |  | 10,492 |  | 8,938 |  |  |
Unrealized losses |  | 27,595 |  | 32,028 |  |  |
Fair value |  | 462,533 |  | 437,869 |  |  |
Allowance |  | 52 |  | 40 |  |  |
Net carrying value |  | 479,584 |  | 460,919 |  |  |
Mortgage-backed Securities-Residential [Member] |  |  |  |  |  |  |
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | 171,074 |  | 138,468 |  |  |
Unrealized gains |  | 1,066 |  | 1,388 |  |  |
Unrealized losses |  | 2,489 |  | 2,327 |  |  |
Fair value |  | 169,651 |  | 137,529 |  |  |
Allowance |  | 0 |  | 0 |  |  |
Net carrying value |  | 171,074 |  | 138,468 |  |  |
Mortgage-backed Securities-Multi-family [Member] |  |  |  |  |  |  |
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | 121,738 |  | 130,119 |  |  |
Unrealized gains |  | 0 |  | 0 |  |  |
Unrealized losses |  | 9,727 |  | 11,963 |  |  |
Fair value |  | 112,011 |  | 118,156 |  |  |
Allowance |  | 0 |  | 0 |  |  |
Net carrying value |  | 121,738 |  | 130,119 |  |  |
Corporate Debt Securities [Member] |  |  |  |  |  |  |
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | 28,500 |  | 31,270 |  |  |
Unrealized gains |  | 166 |  | 55 |  |  |
Unrealized losses |  | 1,066 |  | 1,756 |  |  |
Fair value |  | 27,600 |  | 29,569 |  |  |
Allowance |  | 497 |  | 507 |  |  |
Net carrying value |  | 28,003 |  | 30,763 |  |  |
Other Securities [Member] |  |  |  |  |  |  |
Securities [Abstract] |  |  |  |  |  |  |
Amortized cost, total securities held-to-maturity | [1] | 26 |  | 29 |  |  |
Unrealized gains |  | 0 |  | 0 |  |  |
Unrealized losses |  | 0 |  | 0 |  |  |
Fair value |  | 26 |  | 29 |  |  |
Allowance |  | 1 |  | 1 |  |  |
Net carrying value |  | $ 25 |  | $ 28 |  |  |
[1] | Amortized cost excludes accrued interest receivable of $7.0 million and $4.9 million at March 31, 2026 and June 30, 2025, respectively, which is included in accrued interest receivable in the consolidated statements of financial condition.

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