Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	The Company has prepared the consolidated unaudited interim financial statements included in this report. All intercompany transactions and accounts have been eliminated in consolidation. The preparation of financial statements, in conformity with accounting principles generally accepted in the United States of America (“GAAP”), requires management to make estimates and assumptions that affect amounts reported in the financial statements. Actual results could differ from these estimates. In the opinion of management, all adjustments (consisting only of normal recurring adjustments) necessary for a fair presentation are reflected in the interim financial statements. Certain amounts in the financial statements from prior periods have been reclassified to conform to the current financial statement presentation. The information included in this Form 10-Q should be read in conjunction with the financial statements and related notes in the Company's 2018 Annual Report on Form 10-K (“2018 Annual Financial Statements”). Interim results are not necessarily indicative of results for a full year.
Equity Securities	The Company records equity securities within Other assets in its Consolidated Statements of Financial Condition. Investments in equity securities with readily determinable fair values (marketable) are measured at fair value, with changes in the fair value recognized as a component of Other income in the Consolidated Statements of Operations. Investments in equity investments that do not have readily determinable fair values (non-marketable) are accounted for at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer, also referred to as the measurement alternative. Any adjustments to the carrying value of these investments are recorded in Other income in the Consolidated Statements of Operations.
Off-Balance-Sheet Credit Exposures	The Company estimates losses on off-balance-sheet credit exposures by allocating a loss percentage derived from historical loss factors for each asset class.
New Accounting Pronouncements	In April 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, that clarifies and improves areas of guidance related to the recently issued standards on credit losses (ASU 2016-13), hedging (ASU 2017-12), and recognition and measurement of financial instruments (ASU 2016-01). The amendments generally have the same effective dates as their related standards. If already adopted, the amendments of ASU 2016-01 and ASU 2016-13 are effective for fiscal years beginning after December 15, 2019 and the amendments of ASU 2017-12 are effective as of the beginning of the Company’s next annual reporting period; early adoption is permitted. The Company previously adopted both ASU 2017-12 and ASU 2016-01 and does not expect the amendments of ASU 2019-04 will have a material impact on its consolidated financial statements. The Company is continuing to evaluate the impact of ASU 2016-13 and will consider the amendments of ASU 2019-04 as part of that process. In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That is a Service Contract. The amendments in this ASU align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The amendments also require the entity to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement, including reasonably certain renewal periods. The amendments in the ASU are effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Early adoption is permitted, including adoption in any interim period. The Company is assessing the impact that this guidance will have on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This ASU adds, eliminates, and modifies certain disclosure requirements for fair value measurements. Among the changes, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, but will be required to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. The ASU is effective for interim and annual reporting periods beginning after December 15, 2019; early adoption is permitted. Entities are also allowed to elect early adoption of the eliminated or modified disclosure requirements and delay adoption of the added disclosure requirements until their effective date. As the ASU only revises disclosure requirements, this guidance will not have a material impact on the Company's consolidated financial statements. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) - Targeted Improvements to provide entities with relief from the costs of implementing certain aspects of the new leasing standard, ASU No. 2016-02. Specifically, under the amendments in ASU 2018-11: (1) entities may elect not to recast the comparative periods presented when transitioning to the new leasing standard, and (2) lessors may elect to not separate non-lease components from leases when certain conditions are met. The amendments have the same effective date as ASU 2016-02 (October 1, 2019 for the Company). The Company expects to elect both transition options. ASU 2018-11 is not expected to have a material impact on the Company's consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses. The amendments in this ASU were issued to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments that are not accounted for at fair value through net income, including loans held for investment, held-to-maturity debt securities, trade and other receivables, net investments in leases and other commitments to extend credit held by a reporting entity at each reporting date. The amendments require that financial assets measured at amortized cost be presented at the net amount expected to be collected, through an allowance for credit losses that is deducted from the amortized cost basis. The ASU eliminates the current framework of recognizing probable incurred losses and instead requires an entity to use its current estimate of all expected credit losses over the contractual life. The measurement of expected credit losses is based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the financial assets. For purchased financial assets with a more-than-insignificant amount of credit deterioration since origination (“PCD assets”) that are measured at amortized cost, an allowance for expected credit losses is recorded as an adjustment to the cost basis of the asset. Subsequent changes in estimated cash flows would be recorded as an adjustment to the allowance and through the statement of income. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down to the security's cost basis. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. For most debt securities, the transition approach requires a cumulative-effect adjustment to the statement of financial position as of the beginning of the first reporting period the guidance is effective. For other-than-temporarily impaired debt securities and PCD assets, the guidance will be applied prospectively. While the Company is currently in the process of evaluating the impact of the amended guidance on its consolidated financial statements, it currently expects the ALLL to increase upon adoption given that the allowance will be required to cover the full remaining expected life of the portfolio upon adoption, rather than the incurred loss model under current U.S. GAAP. The extent of this increase is still being evaluated and will depend on economic conditions and the composition of the Company’s loan and lease portfolio at the time of adoption. In February 2016, the FASB issued ASU 2016-02, Leases. The ASU, as amended, requires lessees to recognize a lease liability, which is a lessee's obligation to make lease payments arising from a lease, and a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. The guidance also simplifies the accounting for sale and leaseback transactions and introduces new disclosure requirements for leasing arrangements. Accounting by lessors is largely unchanged. The amendments are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company will adopt the standard effective October 1, 2019. Lessees (for capital and operating leases) and lessors (for sales-type, direct financing, and operating leases) must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. The modified retrospective approach would not require any transition accounting for leases that expired before the earliest comparative period presented. The Company leases a number of properties under non-cancelable operating leases which will be subject to this ASU. We do not expect a material impact to our Consolidated Statement of Operations as a result of this ASU. While the Company has not quantified the impact to its Consolidated Statement of Condition, the Company expects to recognize right-of-use assets and lease liabilities for substantially all of its operating lease commitments based on the present value of unpaid lease payments as of the date of adoption. For information on the Company's future minimum lease payments, refer to Note I Premises and Equipment in our Annual Report on Form 10-K for the year ended September 30, 2018.