Summary Of Significant Accounting Policies	6 Months Ended
Mar. 31, 2025
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation - The consolidated financial statements include the accounts of Capitol Federal Financial, Inc.® (the "Company") and its wholly-owned subsidiary, Capitol Federal Savings Bank (the "Bank"). The Bank has two wholly-owned subsidiaries, Capitol Funds, Inc. and Capital City Investments, Inc. Capitol Funds, Inc. has a wholly-owned subsidiary, Capitol Federal Mortgage Reinsurance Company. Capital City Investments, Inc. is a real estate and investment holding company. All intercompany accounts and transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2024, filed with the Securities and Exchange Commission ("SEC"). Interim results are not necessarily indicative of results for a full year. Net Presentation of Cash Flows Related to Borrowings - At times, the Bank enters into FHLB advances with contractual maturities of 90 days or less. Cash flows related to these advances are reported on a net basis in the consolidated statements of cash flows. Recent Accounting Pronouncements - In October 2023, the Financial Accounting Standards Board ("FASB") issued ASU 2023-06, Disclosure Improvements - Codification Amendments in Response to the SEC's Disclosure Update and Simplification Initiative. This ASU incorporates a variety of Topics into the FASB Accounting Standards Codification (the "Codification") that are currently included in SEC Regulations S-X and S-K. The ASU is intended to align the accounting standards of GAAP with SEC Regulations S-X and S-K. Each amendment in the ASU will only become effective for the Company if the SEC removes the related disclosure or presentation requirement from its existing regulations by June 30, 2027. This may result in disclosures currently presented outside of the Company's financial statements being relocated to the Company's financial statements. The amendments will be applied prospectively by the Company. The ASU is not expected to have a material impact on the Company's disclosures as the Company is currently subject to SEC Regulations S-X and S-K. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures. This ASU requires enhanced disclosures of segment information for all public entities, including those that have a single reportable segment, primarily in the area of segment revenues and expenses. Entities that have a single reportable segment, like the Company, will be required to provide all the disclosures required by this ASU and all existing segment disclosures required by Accounting Standards Codification ("ASC") 280, Segment Reporting. This ASU is effective for fiscal years beginning after December 15, 2023, which is the fiscal year ending September 30, 2025 for the Company, and interim periods within fiscal years beginning after December 15, 2024, which is the quarter ending December 31, 2025 for the Company. The Company is currently evaluating the effect this ASU will have on the Company's segment disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures. This ASU requires public entities to provide additional annual disclosures regarding specific categories of the income tax rate reconciliation and additional information for reconciling items within the income tax rate reconciliation that meet a certain quantitative threshold. This ASU is effective for the Company on October 1, 2025, starting with its Form 10-Q for the quarter ending December 31, 2025. The Company is currently evaluating the effect this ASU will have on the Company's income tax disclosures. In March 2024, the FASB issued ASU 2024-02, Codification Improvements - Amendments to Remove References to the Concepts Statements. This ASU removes references to various Concept Statements to simplify the Codification and provide a distinction between authoritative and nonauthoritative literature. This ASU is effective for the Company on October 1, 2025, starting with its Form 10-K for the fiscal year ending September 30, 2026. The Company is currently evaluating this ASU, but it is not expected to have a significant impact on the Company's consolidated financial condition or results of operation or the Company's disclosures. In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures. This ASU requires additional expense disclosures by public entities in the notes to the financial statements. The ASU outlines the specific costs that are required to be disclosed, which include costs such as: purchases of inventory, employee compensation, depreciation, intangible asset amortization, selling costs, and depreciation, depletion, and amortization related to oil and gas production. It also requires qualitative descriptions of the amounts remaining in the relevant expense income statement captions that are not separately disaggregated quantitatively in the notes to the financial statements and the entity's definition of selling expenses. The disclosures are required for each interim and annual reporting period. The ASU is effective for fiscal years beginning after December 15, 2026, which is the fiscal year ending September 30, 2028 for the Company. In January 2025, the FASB issued ASU 2025-1, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures: Clarifying the Effective Date. The FASB clarified the interim date reporting when an entity adopts ASU 2024-03. Per ASU 2025-01, ASU 2024-03 is effective for interim periods within fiscal years beginning after December 15, 2027, which is the quarter ending December 31, 2028 for the Company. The Company is currently evaluating the effect this ASU will have on the Company's expense disclosures in the notes to the consolidated financial statements.

Basis of Presentation - The consolidated financial statements include the accounts of Capitol Federal Financial, Inc.® (the "Company") and its wholly-owned subsidiary, Capitol Federal Savings Bank (the "Bank"). The Bank has two wholly-owned subsidiaries, Capitol Funds, Inc. and Capital City Investments, Inc. Capitol Funds, Inc. has a wholly-owned subsidiary, Capitol Federal Mortgage Reinsurance Company. Capital City Investments, Inc. is a real estate and investment holding company. All intercompany accounts and transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. These statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2024, filed with the Securities and Exchange Commission ("SEC"). Interim results are not necessarily indicative of results for a full year.

Recent Accounting Pronouncements - In October 2023, the Financial Accounting Standards Board ("FASB") issued ASU 2023-06, Disclosure Improvements - Codification Amendments in Response to the SEC's Disclosure Update and Simplification Initiative. This ASU incorporates a variety of Topics into the FASB Accounting Standards Codification (the "Codification") that are currently included in SEC Regulations S-X and S-K. The ASU is intended to align the accounting standards of GAAP with SEC Regulations S-X and S-K. Each amendment in the ASU will only become effective for the Company if the SEC removes the related disclosure or presentation requirement from its existing regulations by June 30, 2027. This may result in disclosures currently presented outside of the Company's financial statements being relocated to the Company's financial statements. The amendments will be applied prospectively by the Company. The ASU is not expected to have a material impact on the Company's disclosures as the Company is currently subject to SEC Regulations S-X and S-K.

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) - Improvements to Reportable Segment Disclosures. This ASU requires enhanced disclosures of segment information for all public entities, including those that have a single reportable segment, primarily in the area of segment revenues and expenses. Entities that have a single reportable segment, like the Company, will be required to provide all the disclosures required by this ASU and all existing segment disclosures required by Accounting Standards Codification ("ASC") 280, Segment Reporting. This ASU is effective for fiscal years beginning after December 15, 2023, which is the fiscal year ending September 30, 2025 for the Company, and interim periods within fiscal years beginning after December 15, 2024, which is the quarter ending December 31, 2025 for the Company. The Company is currently evaluating the effect this ASU will have on the Company's segment disclosures.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures. This ASU requires public entities to provide additional annual disclosures regarding specific categories of the income tax rate reconciliation and additional information for reconciling items within the income tax rate reconciliation that meet a certain quantitative threshold. This ASU is effective for the Company on October 1, 2025, starting with its Form 10-Q for the quarter ending December 31, 2025. The Company is currently evaluating the effect this ASU will have on the Company's income tax disclosures.

In March 2024, the FASB issued ASU 2024-02, Codification Improvements - Amendments to Remove References to the Concepts Statements. This ASU removes references to various Concept Statements to simplify the Codification and provide a distinction between authoritative and nonauthoritative literature. This ASU is effective for the Company on October 1, 2025, starting with its Form 10-K for the fiscal year ending September 30, 2026. The Company is currently evaluating this ASU, but it is not expected to have a significant impact on the Company's consolidated financial condition or results of operation or the Company's disclosures.

In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures. This ASU requires additional expense disclosures by public entities in the notes to the financial statements. The ASU outlines the specific costs that are required to be disclosed, which include costs such as: purchases of inventory, employee compensation, depreciation, intangible asset amortization, selling costs, and depreciation, depletion, and amortization related to oil and gas production. It also requires qualitative descriptions of the amounts remaining in the relevant expense income statement captions that are not separately disaggregated quantitatively in the notes to the financial statements and the entity's definition of selling expenses. The disclosures are required for each interim and annual reporting period. The ASU is effective for fiscal years beginning after December 15, 2026, which is the fiscal year ending September 30, 2028 for the Company. In January 2025, the FASB issued ASU 2025-1, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures: Clarifying the Effective

Date. The FASB clarified the interim date reporting when an entity adopts ASU 2024-03. Per ASU 2025-01, ASU 2024-03 is effective for interim periods within fiscal years beginning after December 15, 2027, which is the quarter ending December 31, 2028 for the Company. The Company is currently evaluating the effect this ASU will have on the Company's expense disclosures in the notes to the consolidated financial statements.