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v3.25.1

Fair Value Measurements - Securities in Unrealized Loss Positions (Details) $ in Thousands | Mar. 31, 2025 USD ($) security | Sep. 30, 2024 USD ($) security
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Number of debt securities with unrealized loss | security | 205 | 209
Available-for-sale securities |  |
Less than 12 months, unrealized gross losses | $ (1,586) | $ (429)
12 months or more, unrealized gross losses | (63,661) | (54,270)
Total unrealized gross losses | (65,247) | (54,699)
Less than 12 months, fair value | 253,669 | 239,441
12 months or more, fair value | 952,292 | 1,125,962
Total, fair value | 1,205,961 | 1,365,403
Held-to-maturity securities |  |
Less than 12 months, unrealized gross losses | (9) | 0
Less than 12 months, fair value | 34,152 | 0
12 months or more, unrealized gross losses | (42,883) | (36,839)
12 months or more, fair value | 324,360 | 348,573
Total unrealized gross losses | (42,892) | (36,839)
Total, fair value | 358,512 | 348,573
Less than 12 months, unrealized gross losses | (1,595) | (429)
Less than 12 months, fair value | 287,821 | 239,441
12 months or more, unrealized gross losses | (106,544) | (91,109)
12 months or more, fair value | 1,276,652 | 1,474,535
Total unrealized gross losses | (108,139) | (91,538)
Total fair value | 1,564,473 | 1,713,976
Corporate debt securities |  |
Available-for-sale securities |  |
Less than 12 months, unrealized gross losses | (229) | 0
12 months or more, unrealized gross losses | (11,834) | (10,993)
Total unrealized gross losses | (12,063) | (10,993)
Less than 12 months, fair value | 19,771 | 0
12 months or more, fair value | 119,597 | 146,060
Total, fair value | 139,368 | 146,060
Municipal bonds due |  |
Available-for-sale securities |  |
Less than 12 months, unrealized gross losses | 0 | (15)
12 months or more, unrealized gross losses | (669) | (394)
Total unrealized gross losses | (669) | (409)
Less than 12 months, fair value | 0 | 19,985
12 months or more, fair value | 14,779 | 15,088
Total, fair value | 14,779 | 35,073
U.S. government and agency securities |  |
Available-for-sale securities |  |
Less than 12 months, unrealized gross losses | 0 | 0
12 months or more, unrealized gross losses | 0 | 0
Total unrealized gross losses | 0 | 0
Less than 12 months, fair value | 0 | 0
12 months or more, fair value | 0 | 0
Total, fair value | 0 | 0
Asset-backed securities |  |
Available-for-sale securities |  |
Less than 12 months, unrealized gross losses | (694) | (249)
12 months or more, unrealized gross losses | (2,156) | (2,373)
Total unrealized gross losses | (2,850) | (2,622)
Less than 12 months, fair value | 87,482 | 116,173
12 months or more, fair value | 196,342 | 235,846
Total, fair value | 283,824 | 352,019
Mortgage-backed securities |  |
Available-for-sale securities |  |
Less than 12 months, unrealized gross losses | (663) | (165)
12 months or more, unrealized gross losses | (49,002) | (40,510)
Total unrealized gross losses | (49,665) | (40,675)
Less than 12 months, fair value | 146,416 | 103,283
12 months or more, fair value | 621,574 | 728,968
Total, fair value | $ 767,990 | $ 832,251

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