Commitment and Contingencies	6 Months Ended
Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Commitments - The Company’s lease commitments consist primarily of real estate property for branches and office space under various non-cancellable operating leases that expire between 2026 and 2070. The majority of the leases contain renewal options and provisions for increases in rental rates based on a predetermined schedule or an agreed upon index. Financial Instruments with Off-Balance Sheet Risk - Off-balance-sheet credit exposures for the Company include unfunded loan commitments and letters of credit from the FHLB of Des Moines and the FHLB of San Francisco. As of March 31, 2026, the Bank was obligated on FHLB letters of credit totaling $30,500,000 and unfunded loan commitments had a balance of $3,066,873,000 compared to September 30, 2025 when the bank was obligated on FHLB letters of credit totaling $62,606,000 and had unfunded commitments of $2,841,596,000. The reserve for unfunded commitments was $22,500,000 as of March 31, 2026, which is unchanged from September 30, 2025. See Note A "Summary of Significant Accounting Policies" for details regarding the reserve methodology. Legal Proceedings - The Company and its subsidiaries are from time to time defendants in and are threatened with various legal proceedings arising from regular business activities. Management, after consulting with legal counsel, is of the opinion that the ultimate liability, if any, resulting from these pending or threatened actions and proceedings will not have a material effect on the financial statements of the Company. LIHTC Investments - The Company has equity investments as limited partners in LIHTC investment funds which are designed to promote qualified affordable housing projects. These investments provide a return through the generation of income tax credits and other income tax benefits and support the Company's regulatory compliance with the Community Reinvestment Act. The Company has evaluated its LIHTC investments and determined it does not have the ability to exercise significant influence over the operating or financial decisions of the funds. This lack of significant influence due to the Company's role as a limited partners allows the Company to account for its LIHTC investments using the proportional amortization method. The Company records the investments in affordable housing partnerships of $149,253,000 and $157,249,000 as of March 31, 2026 and September 30, 2025, respectively, as a component of other assets on the Consolidated Statements of Financial Condition and uses the proportional amortization method to account for the investments. The Company's unfunded contribution commitments to these investments were $63,128,000 and $73,123,000 as of March 31, 2026 and September 30, 2025, respectively, which are recorded as a component of other liabilities on the Consolidated Statements of Financial Condition. Both the tax benefits and the amortization expense related to these investments are reflected in the provision for income taxes on the Consolidated Statements of Operations.

Lease Commitments - The Company’s lease commitments consist primarily of real estate property for branches and office space under various non-cancellable operating leases that expire between 2026 and 2070. The majority of the leases contain renewal options and provisions for increases in rental rates based on a predetermined schedule or an agreed upon index.

Financial Instruments with Off-Balance Sheet Risk - Off-balance-sheet credit exposures for the Company include unfunded loan commitments and letters of credit from the FHLB of Des Moines and the FHLB of San Francisco. As of March 31, 2026, the Bank was obligated on FHLB letters of credit totaling $30,500,000 and unfunded loan commitments had a balance of $3,066,873,000 compared to September 30, 2025 when the bank was obligated on FHLB letters of credit totaling $62,606,000 and had unfunded commitments of $2,841,596,000. The reserve for unfunded commitments was $22,500,000 as of March 31, 2026, which is unchanged from September 30, 2025. See Note A "Summary of Significant Accounting Policies" for details regarding the reserve methodology.

Legal Proceedings - The Company and its subsidiaries are from time to time defendants in and are threatened with various legal proceedings arising from regular business activities. Management, after consulting with legal counsel, is of the opinion that the ultimate liability, if any, resulting from these pending or threatened actions and proceedings will not have a material effect on the financial statements of the Company.

LIHTC Investments - The Company has equity investments as limited partners in LIHTC investment funds which are designed to promote qualified affordable housing projects. These investments provide a return through the generation of income tax credits and other income tax benefits and support the Company's regulatory compliance with the Community Reinvestment Act. The Company has evaluated its LIHTC investments and determined it does not have the ability to exercise significant influence over the operating or financial decisions of the funds. This lack of significant influence due to the Company's role as a limited partners allows the Company to account for its LIHTC investments using the proportional amortization method.

The Company records the investments in affordable housing partnerships of $149,253,000 and $157,249,000 as of March 31, 2026 and September 30, 2025, respectively, as a component of other assets on the Consolidated Statements of Financial Condition and uses the proportional amortization method to account for the investments. The Company's unfunded contribution commitments to these investments were $63,128,000 and $73,123,000 as of March 31, 2026 and September 30, 2025, respectively, which are recorded as a component of other liabilities on the Consolidated Statements of Financial Condition. Both the tax benefits and the amortization expense related to these investments are reflected in the provision for income taxes on the Consolidated Statements of Operations.