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Fair Value Measurements Fair Value Measurement, Measured On Non-Recurring Basis, Signfiicant Unobservable Inputs, Quantitative Information (Details) - Fair Value, Measurements, Nonrecurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands | Sep. 30, 2018 | Sep. 30, 2017
--- | --- | ---
Impaired Loans [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Assets, Fair Value Disclosure |  | $ 24,428 | $ 10,960
Real estate and other repossessed assets [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Assets, Fair Value Disclosure |  | 6,545 | 6,845
Discounted Cash Flow [Member] | Impaired Loans [Member] | Management knowledge of Industry [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Assets, Fair Value Disclosure |  | 24,428 |
Discounted Cash Flow [Member] | Impaired Loans [Member] | Recoverable oil and gas reserves, forward-looking commodity prices, and estimated operating costs [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Assets, Fair Value Disclosure |  |  | 10,960
Discounted Cash Flow [Member] | Real estate and other repossessed assets [Member] | Recoverable oil and gas reserves, forward-looking commodity prices, and estimated operating costs [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Assets, Fair Value Disclosure |  | $ 6,545 | $ 6,845
Minimum [Member] | Impaired Loans [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance | [1] | 41.00% | 64.00%
Maximum [Member] | Impaired Loans [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance | [1] | 84.00% | 88.00%
Weighted Average [Member] | Impaired Loans [Member] |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |
Fair Value of Impaired Loans as Percentage of Unpaid Principal Balance | [1] | 55.00% | 68.00%
[1] | Represents fair value as a percentage of the unpaid principal balance.

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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