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Fair Value Measurements - Fair Value by Balance Sheet Grouping (Details) - USD ($) $ in Thousands | Dec. 31, 2022 | Sep. 30, 2022
--- | --- | ---
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | $ 2,059,837 | $ 2,051,037
Held-to-maturity securities, at amortized cost | 453,443 | 463,299
FHLB and FRB stock | 133,073 | 95,073
Agency pass-through certificates |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Held-to-maturity securities, at amortized cost | 453,443 | 463,299
Carrying Amount |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 2,059,837 | 2,051,037
Held-to-maturity securities, at amortized cost | 453,443 | 463,299
Carrying Amount | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and cash equivalents | 645,862 | 683,965
Carrying Amount | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
FHLB and FRB stock | 133,073 | 95,073
Time deposits | 3,412,203 | 3,338,043
FHLB advances | 3,075,000 | 2,125,000
Carrying Amount | Level 2 | Client swap program hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 63,383 | 67,260
Other liabilities | 63,383 | 67,260
Carrying Amount | Level 2 | Commercial loan fair value hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 2,446 | 2,517
Carrying Amount | Level 2 | Mortgage loan fair value hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 33,986 | 36,765
Carrying Amount | Level 2 | Borrowings cash flow hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 173,139 | 179,945
Carrying Amount | Level 2 | U.S. government and agency securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 99,889 | 39,354
Carrying Amount | Level 2 | Asset-backed securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 696,572 | 767,001
Carrying Amount | Level 2 | Municipal bonds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 35,054 | 34,962
Carrying Amount | Level 2 | Corporate debt securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 316,487 | 313,757
Carrying Amount | Level 2 | Agency pass-through certificates |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 911,835 | 895,963
Held-to-maturity securities, at amortized cost | 453,443 | 463,299
Carrying Amount | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Loans receivable | 16,993,588 | 16,113,564
Estimated Fair Value |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 2,059,837 | 2,051,037
Held-to-maturity securities, at amortized cost | 402,055 | 406,860
Estimated Fair Value | Level 1 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and cash equivalents | 645,862 | 683,965
Estimated Fair Value | Level 2 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
FHLB and FRB stock | 133,073 | 95,073
Time deposits | 3,329,708 | 3,249,169
FHLB advances | 3,067,487 | 1,940,813
Estimated Fair Value | Level 2 | Client swap program hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 63,383 | 67,260
Other liabilities | 63,383 | 67,260
Estimated Fair Value | Level 2 | Commercial loan fair value hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 2,446 | 2,517
Estimated Fair Value | Level 2 | Mortgage loan fair value hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 33,986 | 36,765
Estimated Fair Value | Level 2 | Borrowings cash flow hedges |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Other assets | 173,139 | 179,945
Estimated Fair Value | Level 2 | U.S. government and agency securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 99,889 | 39,354
Estimated Fair Value | Level 2 | Asset-backed securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 696,572 | 767,001
Estimated Fair Value | Level 2 | Municipal bonds |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 35,054 | 34,962
Estimated Fair Value | Level 2 | Corporate debt securities |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 316,487 | 313,757
Estimated Fair Value | Level 2 | Agency pass-through certificates |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale securities, at fair value | 911,835 | 895,963
Held-to-maturity securities, at amortized cost | 402,055 | 406,860
Estimated Fair Value | Level 3 |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Loans receivable | $ 16,310,687 | $ 15,417,635

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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- Definition Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
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- Definition Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits. + References No definition available. + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 22 -URI https://asc.fasb.org/extlink&oid=99393222&loc=SL20226052-175313 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI https://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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- Definition Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=123599499&loc=d3e63345-112809 + Details
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