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Investment Securities - Investments by Contractual Maturity Date (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Sep. 30, 2022
--- | --- | ---
Amortized Cost, Available-for-sale securities |  |
Amortized cost | $ 2,118,616 | $ 2,162,737
Gross Unrealized Gains / Losses, Available-for-sale securities |  |
Gross unrealized gains | 2,910 | 1,308
Gross unrealized loss | (126,429) | (113,008)
Fair Value, Available-for-sale securities |  |
Available-for-sale securities, at fair value | $ 1,995,097 | $ 2,051,037
Yield, Available-for-sale securities |  |
Yield | 4.64% | 3.36%
Amortized Cost, Held-to-maturity securities |  |
Held-to-maturity securities, amortized cost | $ 423,586 | $ 463,299
Gross Unrealized Gains / Losses, Held-to-maturity securities |  |
Gross unrealized gains | 0 | 22
Gross unrealized losses | (68,398) | (56,461)
Fair Value, Held-to-maturity securities |  |
Fair value | $ 355,188 | $ 406,860
Yield, Held-to-maturity securities |  |
Without single maturity date |  | 2.88%
Yield | 2.88% |
Investments | $ 2,542,202 | $ 2,626,036
Gross unrealized gains on investments | 2,910 | 1,330
Gross unrealized losses on investments | (194,827) | (169,469)
Total Financial Assets | $ 2,350,285 | $ 2,457,897
Yield on investments | 4.35% | 3.28%
U.S. government and agency securities due |  |
Amortized Cost, Available-for-sale securities |  |
Within 1 year | $ 3,501 |
1 to 5 years | 18,894 | $ 40,403
5 to 10 years | 87,922 |
Over 10 years | 106,340 |
Gross Unrealized Gains / Losses, Available-for-sale securities |  |
Gross unrealized gains, within 1 year | 0 |
Gross unrealized gains, 1 to 5 years | 0 | 0
Gross unrealized gains, 5 to 10 years | 177 |
Gross unrealized gains, over 10 years | 831 |
Gross unrealized losses, within 1 year | (36) |
Gross unrealized losses, 1 to 5 years | (563) | (1,049)
Gross unrealized losses, 5 to 10 years | 0 |
Gross unrealized losses, over 10 years | (13) |
Fair Value, Available-for-sale securities |  |
Within 1 year | 3,465 |
1 to 5 years | 18,331 | $ 39,354
5 to 10 years | 88,099 |
Over 10 years | $ 107,158 |
Yield, Available-for-sale securities |  |
Within 1 year | 6.06% |
1 to 5 years | 4.70% | 3.03%
5 to 10 years | 5.76% |
Over 10 years | 5.84% |
Asset-backed securities due |  |
Amortized Cost, Available-for-sale securities |  |
1 to 5 years | $ 18,579 | $ 22,527
5 to 10 years | 36,875 | 82,962
Over 10 years | 539,911 | 668,482
Gross Unrealized Gains / Losses, Available-for-sale securities |  |
Gross unrealized gains, 1 to 5 years | 0 | 0
Gross unrealized gains, 5 to 10 years | 2 | 4
Gross unrealized gains, over 10 years | 578 | 783
Gross unrealized losses, 1 to 5 years | (715) | (1,141)
Gross unrealized losses, 5 to 10 years | (99) | (547)
Gross unrealized losses, over 10 years | (7,115) | (6,069)
Fair Value, Available-for-sale securities |  |
1 to 5 years | 17,864 | 21,386
5 to 10 years | 36,778 | 82,419
Over 10 years | $ 533,374 | $ 663,196
Yield, Available-for-sale securities |  |
1 to 5 years | 6.06% | 3.27%
5 to 10 years | 6.11% | 3.53%
Over 10 years | 6.35% | 3.86%
Corporate debt securities |  |
Amortized Cost, Available-for-sale securities |  |
Within 1 year |  | $ 75,000
1 to 5 years | $ 151,893 | 151,411
5 to 10 years | 113,221 | 114,414
Gross Unrealized Gains / Losses, Available-for-sale securities |  |
Gross unrealized gains, within 1 year |  | 4
Gross unrealized gains, 1 to 5 years | 895 | 0
Gross unrealized gains, 5 to 10 years | 0 | 0
Gross unrealized losses, within 1 year |  | (200)
Gross unrealized losses, 1 to 5 years | (1,787) | (2,748)
Gross unrealized losses, 5 to 10 years | (21,700) | (24,124)
Fair Value, Available-for-sale securities |  |
Within 1 year |  | 74,804
1 to 5 years | 151,001 | 148,663
5 to 10 years | $ 91,521 | $ 90,290
Yield, Available-for-sale securities |  |
Within 1 year |  | 3.74%
1 to 5 years | 5.14% | 3.59%
5 to 10 years | 3.87% | 3.87%
Municipal bonds |  |
Amortized Cost, Available-for-sale securities |  |
5 to 10 years | $ 5,720 | $ 5,751
Over 10 years | 29,832 | 29,871
Gross Unrealized Gains / Losses, Available-for-sale securities |  |
Gross unrealized gains, 5 to 10 years | 0 | 0
Gross unrealized gains, over 10 years | 361 | 400
Gross unrealized losses, 5 to 10 years | (701) | (361)
Gross unrealized losses, over 10 years | (550) | (699)
Fair Value, Available-for-sale securities |  |
5 to 10 years | 5,019 | 5,390
Over 10 years | $ 29,643 | $ 29,572
Yield, Available-for-sale securities |  |
5 to 10 years | 3.00% | 3.00%
Over 10 years | 5.85% | 5.85%
Agency pass-through certificates |  |
Amortized Cost, Available-for-sale securities |  |
Without single maturity date | $ 1,005,928 | $ 971,916
Gross Unrealized Gains / Losses, Available-for-sale securities |  |
Gross unrealized gains, without single maturity date | 66 | 117
Gross unrealized losses, without single maturity date | (93,150) | (76,070)
Fair Value, Available-for-sale securities |  |
Without single maturity date | $ 912,844 | $ 895,963
Yield, Available-for-sale securities |  |
Without single maturity date | 3.39% | 2.81%
Amortized Cost, Held-to-maturity securities |  |
Without single maturity date | $ 423,586 | $ 463,299
Gross Unrealized Gains / Losses, Held-to-maturity securities |  |
Gross unrealized gains, without single maturity date | 0 | 22
Gross unrealized losses, without single maturity date | (68,398) | (56,461)
Fair Value, Held-to-maturity securities |  |
Without single maturity date | $ 355,188 | $ 406,860
Yield, Held-to-maturity securities |  |
Without single maturity date | 2.88% | 2.88%

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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-3 + Details
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