Fair Value Measurements Fair Value Measurement, Measured On Non-Recurring Basis, Signfiicant Unobservable Inputs, Quantitative Information (Details) - Fair Value, Nonrecurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Impaired Loans [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 9,810	$ 24,428
Real estate and other repossessed assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	936	6,545
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	9,810	24,428
Discounted Cash Flow [Member] | Real estate and other repossessed assets [Member] | Marketability adjustments off appraised value
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assets, Fair Value Disclosure	$ 936
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
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	8.00%	41.00%
Minimum [Member] | Real estate and other repossessed assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Measurement, Percentage of Appraised Value. Minimum	75.00%
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	76.00%	84.00%
Maximum [Member] | Real estate and other repossessed assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Measurement, Percentage of Appraised Value. Minimum	89.00%
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	28.00%	55.00%
Weighted Average [Member] | Real estate and other repossessed assets [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value Measurement, Percentage of Appraised Value. Minimum	85.00%