Great Western Bancorp (GWB) 10-Q 9 Feb 21 2021 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Dec. 31, 2020	Jan. 28, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-36688
Entity Registrant Name	Great Western Bancorp, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-1308512
Entity Address, Address Line One	225 South Main Avenue
Entity Address, City or Town	Sioux Falls,
Entity Address, State or Province	SD
Entity Address, Postal Zip Code	57104
City Area Code	605
Local Phone Number	334-2548
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	GWB
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (shares)		55,105,304
Entity Central Index Key	0001613665
Current Fiscal Year End Date	--09-30
Document Fiscal Year Focus	2021
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q1
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2020	Sep. 30, 2020
Assets
Cash and due from banks		$ 228,050	$ 150,085
Interest-bearing bank deposits		833,746	282,802
Cash and cash equivalents		1,061,796	432,887
Securities available for sale		2,059,615	1,774,626
Loans, net of unearned discounts and deferred fees, including $611,588 and $655,185 of loans at fair value under the fair value option at December 31, 2020 and September 30, 2020, respectively; and $11,638 and $12,371 of loans held for sale at December 31, 2020 and September 30, 2020, respectively		9,517,876	10,076,142
Allowance for credit losses	[1]	(308,794)	(149,887)
Net loans		9,209,082	9,926,255
Premises and equipment, including $600 of property held for sale at both December 31, 2020 and September 30, 2020		119,362	119,054
Accrued interest receivable		47,598	54,658
Other repossessed property		18,086	20,034
Cash surrender value of life insurance policies		31,873	31,658
Net deferred tax assets		91,704	47,709
Other assets		175,267	197,558
Total assets		12,814,383	12,604,439
Deposits
Noninterest-bearing		2,858,455	2,586,743
Interest-bearing		8,514,863	8,422,036
Total deposits		11,373,318	11,008,779
Securities sold under agreements to repurchase		80,355	65,506
FHLB advances and other borrowings		120,000	195,000
Subordinated debentures and subordinated notes payable		108,866	108,832
Accrued expenses and other liabilities		63,343	63,389
Total liabilities		11,745,882	11,441,506
Stockholders’ equity
Common stock, $0.01 par value, authorized 500,000,000 shares; 55,105,105 shares issued and outstanding at December 31, 2020 and 55,014,189 shares issued and outstanding at September 30, 2020		550	550
Additional paid-in capital		1,184,281	1,183,647
Retained earnings		(148,769)	(57,169)
Accumulated other comprehensive income		32,439	35,905
Total stockholders' equity		1,068,501	1,162,933
Total liabilities and stockholders' equity		$ 12,814,383	$ 12,604,439
[1]	Prior to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020, this line represented the allowance for loan and lease losses under the incurred loss model.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Assets
Loans at fair value under the fair value option	$ 611,588	$ 655,185
Loan held for sale	11,638	12,371
Property held for sale	$ 600	$ 600
Stockholders’ equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	55,105,105	55,014,189
Common stock, shares outstanding (in shares)	55,105,105	55,014,189

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Interest income
Loans		$ 107,323	$ 119,431
Investment securities		8,119	11,498
Federal funds sold and other		155	608
Total interest income		115,597	131,537
Interest expense
Deposits		5,992	21,940
FHLB advances and other borrowings		880	3,113
Subordinated debentures and subordinated notes payable		817	1,311
Total interest expense		7,689	26,364
Net interest income		107,908	105,173
Provision for credit losses	[1],[2]	11,899	8,103
Net interest income after provision for credit losses		96,009	97,070
Noninterest income
Service charges and other fees		9,624	11,409
Wealth management fees		3,029	2,964
Mortgage banking income, net		4,090	1,612
Net gain on sale of securities and other assets		248	0
Derivative interest expense		(3,393)	(890)
Change in fair value of FVO loans and related derivatives		(1,672)	(2,124)
Other derivative income		898	1,597
Other		1,324	1,165
Total noninterest income		14,148	15,733
Noninterest expense
Salaries and employee benefits		37,554	35,905
Data processing and communication		6,226	5,773
Occupancy and equipment		5,213	5,093
Professional fees		3,915	3,764
Advertising		556	865
Net loss on repossessed property and other related expenses		345	342
Other		3,640	5,188
Total noninterest expense		57,449	56,930
Income before income taxes		52,708	55,873
Provision for income taxes		11,389	12,599
Net income		$ 41,319	$ 43,274
Basic earnings per common share
Weighted average shares outstanding (in shares)		55,119,909	56,377,631
Earnings per share (in dollars per share)		$ 0.75	$ 0.77
Diluted earnings per common share
Weighted average shares outstanding (in shares)		55,247,343	56,457,967
Diluted earnings per share (in dollars per share)		$ 0.75	$ 0.77
Dividends per share
Dividends paid		$ 550	$ 16,885
Dividends per share (in dollars per share)		$ 0.01	$ 0.30
[1]	For the three months ended December 31, 2020, this line includes a $(0.1) million (reversal of) provision for unfunded commitment reserve. For the three months ended December 31, 2019, provision for unfunded commitment reserve of $0.2 million was recorded in other noninterest expense in the consolidated income statement.
[2]	For the three months ended December 31, 2020, this line includes a $0.1 million decrease in unfunded commitment reserve.

Consolidated Statements of In_2

Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
(Reversal of) provision for unfunded commitments	$ (0.1)	$ 0.2

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 41,319	$ 43,274
Securities available for sale:
Net unrealized holding loss arising during the period	(4,352)	(8,160)
Reclassification adjustment for net gain realized in net income	(248)	0
Income tax benefit	1,134	2,010
Other comprehensive loss, net of tax	(3,466)	(6,150)
Comprehensive income	$ 37,853	$ 37,124

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Cumulative effect adjustment related to ASU adoption		Common Stock Par Value	Additional Paid-in Capital	Retained Earnings	Retained EarningsCumulative effect adjustment related to ASU adoption		Accumulated Other Comprehensive Income
Beginning balance at Sep. 30, 2019		$ 1,900,249	$ (182)	[1]	$ 563	$ 1,228,714	$ 657,475	$ (182)	[1]	$ 13,497
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		43,274					43,274
Other comprehensive (loss), net of tax		(6,150)								(6,150)
Comprehensive income		37,124
Stock-based compensation, net of tax		363				363
Common stock cash dividends		(16,885)					(16,885)
Ending balance at Dec. 31, 2019		1,920,669			563	1,229,077	683,682			7,347
Beginning balance at Sep. 30, 2019		$ 1,900,249	(182)	[1]	563	1,228,714	657,475	(182)	[1]	13,497
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	[2]	us-gaap:AccountingStandardsUpdate201613Member
Ending balance at Sep. 30, 2020		$ 1,162,933	$ (132,919)	[2]	550	1,183,647	(57,169)	$ (132,919)	[2]	35,905
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		41,319					41,319
Other comprehensive (loss), net of tax		(3,466)								(3,466)
Comprehensive income		37,853
Stock-based compensation, net of tax		1,184				1,184
Common stock cash dividends		(550)				(550)
Ending balance at Dec. 31, 2020		$ 1,068,501			$ 550	$ 1,184,281	$ (148,769)			$ 32,439
[1]	Cumulative effect adjustment related to the Company's adoption of ASU 2016-02 and subsequent related ASUs on October 1, 2019.
[2]	Cumulative effect adjustment related to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020. For additional information, see Note 2, " New Accounting Pronouncements ".

Consolidated Statement of Sto_2

Consolidated Statement of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Cash dividends paid on common stock (in dollars per share)	$ 0.01	$ 0.30

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($)		3 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net income		$ 41,319,000	$ 43,274,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		4,778,000	3,947,000
Amortization of FDIC indemnification asset		0	251,000
Net gain on sale of other assets		(605,000)	0
Net gain on sale of loans		(4,330,000)	(1,814,000)
Provision for credit losses	[1],[2]	11,899,000	8,103,000
Provision for loan servicing rights loss		0	1,000
Stock-based compensation		1,184,000	363,000
Originations of residential real estate loans held for sale		(132,118,000)	(105,185,000)
Proceeds from sales of residential real estate loans held for sale		137,182,000	108,816,000
Proceeds from sale of other assets		348,000	0
Net deferred income taxes		11,000	(6,626,000)
Changes in:
Accrued interest receivable		7,060,000	3,722,000
Other assets		21,358,000	(71,000)
Accrued interest payable and other liabilities		510,000	23,674,000
Net cash provided by operating activities		88,596,000	78,455,000
Investing activities
Purchase of securities available for sale		(487,816,000)	(247,934,000)
Proceeds from sales of securities available for sale		0	0
Proceeds from maturities of securities available for sale		195,585,000	117,333,000
Net decrease in loans		528,843,000	65,253,000
Payment of covered losses from FDIC indemnification claims		0	(4,000)
Purchase of premises and equipment		(2,110,000)	(2,033,000)
Proceeds from sale of repossessed property		2,313,000	4,569,000
Purchase of FHLB stock		(10,000)	(29,687,000)
Proceeds from redemption of FHLB stock		127,000	20,342,000
Net cash paid in business acquisition		0	(4,711,000)
Net cash provided by (used in) investing activities		236,932,000	(76,872,000)
Financing activities
Net increase (decrease) in deposits		364,561,000	(211,780,000)
Net increase (decrease) in securities sold under agreements to repurchase and other short-term borrowings		14,849,000	(2,703,000)
Proceeds from FHLB advances and other long-term borrowings		0	250,000,000
Repayments on FHLB advances and other long-term borrowings		(75,000,000)	(15,000,000)
Taxes paid related to net share settlement of equity awards		(479,000)	(1,268,000)
Dividends paid		(550,000)	(16,885,000)
Net cash provided by financing activities		303,381,000	2,364,000
Net increase in cash and cash equivalents		628,909,000	3,947,000
Cash and cash equivalents, beginning of period		432,887,000	243,474,000
Cash and cash equivalents, end of period		1,061,796,000	247,421,000
Supplemental disclosure of cash flow information
Cash payments for interest		8,741,000	26,959,000
Cash (receipts from) payments for income taxes		(47,000)	232,000
Supplemental disclosure of noncash investing and financing activities
Loans transferred to repossessed properties		$ 0	$ (7,295,000)
[1]	For the three months ended December 31, 2020, this line includes a $(0.1) million (reversal of) provision for unfunded commitment reserve. For the three months ended December 31, 2019, provision for unfunded commitment reserve of $0.2 million was recorded in other noninterest expense in the consolidated income statement.
[2]	For the three months ended December 31, 2020, this line includes a $0.1 million decrease in unfunded commitment reserve.

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
(Reversal of) provision for unfunded commitments	$ (0.1)	$ 0.2

Nature of Operations and Summar

Nature of Operations and Summary of Significant Policies	3 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Nature of Operations and Summary of Significant Policies	Nature of Operations and Summary of Significant Policies Nature of Operations The Company is a bank holding company organized under the laws of Delaware and is listed on the NYSE under the symbol "GWB." The primary business of the Company is ownership of its wholly-owned subsidiary, Great Western Bank. The Bank is a full-service regional bank focused on relationship-based business and agri-business banking in Arizona, Colorado, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota and South Dakota. Substantially all of the Company's income is generated from banking operations. The Company and the Bank are subject to the regulation of certain federal and/or state agencies and undergo periodic examinations by those regulatory authorities. Basis of Presentation The accompanying unaudited consolidated interim financial statements have been prepared in accordance with GAAP and reflect all adjustments that are, in the opinion of management, necessary for the fair presentation of the financial position and results of operations for the periods presented. All such adjustments are of a normal recurring nature. Certain previously reported amounts have been reclassified to conform to the current presentation. The unaudited interim consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements for the year ended September 30, 2020, which includes a description of significant accounting policies. The results of operations for interim periods are not necessarily indicative of the results that may be expected for the year or any other period. The accompanying unaudited consolidated financial statements include the accounts and results of operations of the Company and its subsidiaries after elimination of all significant intercompany accounts and transactions. The preparation of unaudited consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the amounts reported on the consolidated financial statements and accompanying notes. Actual results could differ from these estimates. Changes in Significant Accounting Policies Pursuant to the Company's adoption of ASU 2016-13, as amended, as of October 1, 2020, the Company updated its accounting policies related to securities, loans and allowance for credit losses. See "Note 2. New Accounting Standards" for additional information on the adoption of the standard. See "Note 3. Securities Available for Sale" and "Note 4. Loans and Allowance for Credit Losses" for new disclosures and additional policy information. There were no other significant changes to the Company's accounting policies from those disclosed in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2020 that could have a material effect on the Company's consolidated financial statements. Securities Purchases and sales of securities are recognized on a trade date basis. The cost of securities sold is based on the specific identification method. The Company classifies securities upon purchase in one of three categories: trading, held to maturity, or available for sale. Debt securities held for resale are classified as trading. Debt securities for which the Company has the ability and positive intent to hold until maturity are classified as held to maturity. All other securities are classified as available for sale as they may be sold prior to maturity in response to changes in the Company’s interest rate risk profile, funding needs, demand for collateralized deposits by public entities or other reasons. Interest and dividends, including amortization of premiums and accretion of discounts, are recognized as interest income when earned. Trading securities are stated at fair value. Realized and unrealized gains and losses from sales and fair value adjustments of trading securities are included in other noninterest income on the consolidated statements of income. Available for sale securities are stated at fair value. For available for sale debt securities in an unrealized loss position, management first evaluates whether (1) the Company has the intent to sell a security; or (2) it is more-likely-than-not that the Company will be required to sell the security before recovery of its amortized cost basis. If either criteria is met, the entire amount of unrealized loss is recognized in the consolidated income statement with a corresponding adjustment to the security's amortized cost basis. If neither criteria is met, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. Furthermore, securities issued by the U.S. Government or a U.S. Government sponsored enterprise which carry the explicit or implicit guarantee of the U.S. Government are considered "risk-free" and therefore no credit losses are assumed on those securities. If the assessment indicates a credit loss exists, the amortized cost basis is compared to the present value of cash flows expected to be collected from the security; if it is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded. Changes in the allowance for credit losses are recorded as a provision for (reversal of) credit losses in the consolidated income statement. If the assessment indicates a credit loss does not exist, the change in fair value is recorded as unrealized gains and losses, net of related taxes, and is included in stockholders’ equity as a component of accumulated other comprehensive income (loss). Equity securities are carried at fair value, with changes in fair value reported in the consolidated statements of income. Equity securities without readily determinable fair values are carried at cost, minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment. Loans Originated Loans Loans that management has the intent and ability to hold for the foreseeable future, or until maturity or pay-off, are reported at amortized cost (i.e., outstanding principal balance, adjusted for charge-offs and any unamortized deferred fees or costs). Other fees not associated with originating a loan are recognized as fee income when earned. Interest income on loans is accrued daily on the outstanding balances. A loan is placed on nonaccrual status when management believes, after considering collection efforts and other factors, the borrower's condition is such that collection of interest is doubtful, which is generally 90 days past due. When loans are placed on nonaccrual status, accrual of interest is discontinued and interest receivable is reversed against interest income in the current period. Interest payments received thereafter are applied as a reduction to the remaining principal balance as long as concern exists as to the ultimate collection of the principal. Loans are removed from nonaccrual status when they become current as to both principal and interest and concern no longer exists as to the collectability of principal and interest. For loans held for sale, loan fees charged or received on origination, net of certain direct loan origination costs, are recognized in income when the related loan is sold. For loans held for investment, loan fees, net of certain direct loan origination costs, are deferred and the net amount is amortized as an adjustment of the related loan’s yield. The Company is generally amortizing these amounts over the contractual lives of the loans. Commitment fees are recognized as income when received. The Company makes commercial, agricultural, residential real estate, consumer and other loans to customers primarily in Arizona, Colorado, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota and South Dakota. The amount of collateral obtained, if deemed necessary, is based on management’s credit evaluation of the borrower. Collateral held varies but includes accounts receivable, marketable securities, inventory, equipment and real estate. Personal guarantees of the borrower or related parties and government guarantees are also obtained for some loans, which reduces the Company’s risk of loss. Loans originated and intended for sale in the secondary market are carried at the lower of cost or fair value. Loans held for sale include fixed rate single-family residential mortgage loans under contract to be sold in the secondary market. In most cases, loans are carried at cost and sold within 45 days. These loans are sold with the mortgage servicing rights released. Under limited circumstances, buyers may have recourse to return a purchased loan to the Company. Recourse conditions may include early payment default, breach of representation or warranties, or documentation deficiencies. Fair value of loans held for sale is determined based on prevailing market prices for loans with similar characteristics, sale contract prices, or, for certain portfolios, discounted cash flow analysis. Declines in fair value below cost (and subsequent recoveries) are recognized in net gain on sale of loans. Deferred fees and costs related to these loans are not amortized but are recognized as part of the cost basis of the loan at the time it is sold. Gains or losses on sales are recognized upon delivery and included in net gain on sale of loans. Loans at Fair Value Under the Fair Value Option ("FVO loans") The Company has elected to measure certain long-term loans and written loan commitments at fair value to assist in managing interest rate risk for longer-term loans. Fair value loans are fixed-rate loans having original maturities of 5 years or greater (typically between 5 and 15 years) to our business and agri-business banking customers to assist them in facilitating their risk management strategies. The fair value option was elected upon the origination or acquisition of these loans and written loan commitments. Interest income is recognized in the same manner on loans reported at fair value as on non-fair value loans, except in regard to origination fees and costs which are recognized immediately upon closing. The Company has also entered into interest rate derivative contracts to convert these long term fixed rate loans to variable rates. These contracts do not quality for hedge accounting and instead these interest rate derivative instruments are recognized as other assets or other liabilities on the consolidated balance sheets and measured at fair value, with changes in fair value reported in change in fair value of FVO loans and related derivatives on the consolidated statements of income. Since each fixed rate loan is paired with an offsetting derivative contract, the impact to net income is minimized. When determined necessary, a credit mark is applied against the valuation of the asset that reflects the borrower's credit worthiness. Changes in the credit mark are included in change in fair value of FVO loans and related derivatives on the consolidated statements of income. Credit Risk Management The Company uses several credit quality indicators to manage credit risk in an ongoing manner. The Company’s strategy for credit risk management includes well-defined, centralized credit policies, uniform underwriting criteria and ongoing risk monitoring and review processes for all credit exposures. The strategy also emphasizes diversification on a geographic, industry, loan class type, and customer level; regular credit examinations; and management reviews of loans exhibiting deterioration of credit quality. The credit risk management strategy also includes a credit risk assessment process that performs assessments of compliance with commercial and consumer credit policies, risk ratings, and other critical credit information. Loan decisions are documented with respect to the borrower’s business, purpose of the loan, evaluation of the repayment sources, and the associated risks, evaluation of collateral, covenants and monitoring requirements, and risk rating rationale. The Company assigns all non-consumer loans a credit quality risk rating. The Company implemented a more granular risk rating methodology as of October 1, 2020. See the table below for a summary of credit quality risk ratings at December 31, 2020. For information on the credit quality risk ratings in effect before October 1, 2020, see "1. Nature of Operations and Summary of Significant Accounting Policies" in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. Credit Quality Credit Quality Indicators Pass Commercial loans within this category are not adversely rated, current as to principal and interest, and are otherwise in compliance with the contractual terms of the loan agreement. Management believes there is a low likelihood of loss related to loans in this category. Special Mention Commercial loans within this category have potential weaknesses that deserve management's close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or in the Company's credit position at some future date. Special mention assets are not adversely classified and do not expose the Company to sufficient risk to warrant an adverse classification. Substandard Commercial loans within this category are inadequately protected by the current sound worth and paying capacity of the borrower or of the collateral pledged, if any. Assets so classified must have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans in this category are assigned a workout loan officer to closely monitor the relationship. Doubtful Commercial loans within this category are considered uncollectible and of such little value that their continuance as bankable assets is not warranted. This classification does not mean that the asset has absolutely no recovery or salvage value, but rather that it is not practical or desirable to defer writing off this basically worthless asset even though partial recovery may be effected in the future. Revolving lines of credit rated Substandard or Doubtful require a higher level of approval and are reviewed quarterly. Advances are allowed to support the continued operating needs of the borrower for their operation and may include, but not limited to, working capital needs to support inventory, accounts receivable, payroll, tax payments, utilities and other needs to operate the business. All non-consumer loan risk ratings are monitored by management and updated as deemed appropriate. The Company generally does not risk rate residential real estate or consumer loans unless a default event such as bankruptcy or extended nonperformance takes place. Alternatively, delinquencies are monitored and standard credit scoring systems are used to assess credit risks of residential real estate and consumer loans. Troubled Debt Restructurings Loans modified under troubled debt restructurings involve granting a concession to a borrower who is experiencing financial difficulty. These concessions could include a reduction in the interest rate on the loan, payment extensions, forgiveness of principal, forbearance, or other actions intended to maximize collection, which generally would not otherwise be considered. The Company's TDRs include performing and nonperforming TDRs, which consist of loans that continue to accrue interest at the loan's original interest rate when the Company expects to collect the remaining principal and interest on the loan, and nonaccrual TDRs, which include loans that are in a nonaccrual status and are no longer accruing interest, as the Company does not expect to collect the full amount of principal and interest owed from the borrower on these loans. At the time of modification (except for loans on nonaccrual status), a TDR is classified as nonperforming TDR until a six-month payment history of principal and interest payments, in accordance with the terms of the loan modification, is sustained, at which time the loan is moved to a performing status (performing TDR). If the Company does not expect to collect all principal and interest on the loan, the modified loan is classified as a nonaccrual TDR. All TDRs are accounted for as impaired loans and are included in the analysis of the allowance for credit losses. A TDR that has been renewed for a borrower who is no longer experiencing financial difficulty and which yields a market rate of interest at the time of a renewal is no longer considered a TDR. In March 2020, a statement was issued by our banking regulators titled "Interagency Statement on Loan Modifications and Reporting for Financial Institutions Working with Customers Affected by the Coronavirus" that encourages financial institutions to work prudently with borrowers who are or may be unable to meet their contractual payment obligations due to the effects of COVID-19. Additionally, Section 4013 of the CARES Act further provides that a qualified loan modification is exempt by law from classification as a TDR as defined by GAAP, from the period beginning March 1, 2020 until December 31, 2020. In December 2020, the Economic Aid to Hard Hit Small Businesses, Non-Profits, and Ventures Act was enacted, which extended the TDR provisions of the CARES Act to January 1, 2022. Accordingly, we are offering short-term modifications made in response to COVID-19 to borrowers who are current and otherwise not past due. These include short-term, 180 days or less, modifications in the form of payment deferrals, fee waivers, extensions of repayment terms, or other delays in payment that are insignificant. Allowance for Credit Losses ("ACL") The Company adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, and subsequent related ASUs, on October 1, 2020, which uses the current expected credit loss model ("CECL") to determine the allowance for credit losses based on an ongoing evaluation, driven primarily by monitoring changes in loan risk grades, delinquencies, and other credit risk indicators, which are inherently subjective. The measurement of expected credit losses under the CECL methodology is applicable to financial assets measured at amortized cost, including loans receivables and held-to-maturity debt securities. It also applies to off-balance sheet credit exposures not accounted for as insurance (loan commitments, standby letters of credit, financial guarantees, and other similar instruments) and the net investments in leases recognized by a lessor in accordance with Topic 842 on leases. The CECL methodology requires recognition of lifetime expected credit losses that takes into consideration all relevant information, including historical losses, current conditions and reasonable and supportable forecasts of future operating conditions. Loans that do not share similar risk characteristics and are collateral dependent, primarily large loans on nonaccrual status and those which have undergone a TDR, are evaluated on an individual basis ("individual reserve"). The reserve related to these loans is using the collateral available to repay the loan, most typically the liquidation value of the collateral (less selling costs, if applicable). The Company has chosen to continue to include small, less complex loans within the collective reserve for loans on nonaccrual or with TDR status. Loans that are not reserved for on an individual basis are measured on a collective, or pooled basis ("collective reserve"). Loans are aggregated into pools (or segments) based on similar risk characteristics including borrower type, collateral, type and expected credit loss patterns. The historical loss experience of the pool is generally the starting point for estimating expected credit losses under the collective reserve methodology. The historical loss experience rate of the loan segment is applied to each loan within the segment over the contractual life of each loan, adjusted for estimated prepayments. Management then determines an appropriate macroeconomic forecast based on the expectation of future conditions, including but not limited to the unemployment rate, which is the most significant factor, gross domestic product and corporate bond spreads, and applies the forecast to models which estimate the change in loss expectations relative to the historical loss rates. These models have been implemented in accordance with the Company's Model Risk Management Policy. Additionally, using its new risk rating system, the Company evaluates if the current credit quality of the portfolio materially differs from the one observed over the historical loss period and applies adjustments to the allowance accordingly. Qualitative adjustments may also be made to expected losses based on current and future conditions that may not be fully captured in the modeling components above, such as but not limited to industry, geographic and borrower concentrations, loans servicing practices and changes in underwriting criteria. ASU 2016-13 requires institutions to establish a supportable forecast and reversion period for forecasted operating conditions. Management determined a two-year forecast period would capture the majority of the impact associated with current economic conditions and is short enough to be supportable. Additionally, loss rate forecasts follow a straight-line reversion back to the historical loss rate over one year following the initial forecast period. The following table describes the Company’s eight loan portfolio pools, which is the level at which it develops and documents a systematic methodology to determine the allowance for credit losses. Loan Segment Composition Collateral Primary Source of Repayment Key Risk Characteristics Construction and development 1 Commercial and residential construction loans Secured by commercial and residential real estate Cash flows Industry and geography of borrower's business, purpose of the loan, repayment sources, borrower's capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Owner-occupied CRE Small and middle market businesses Secured by commercial real estate Non-owner-occupied CRE Multifamily residential real estate Agriculture Agri-business operating and real estate loans Secured by operating assets, agricultural real estate, and guarantees of owners Cash flows Geography of the borrower's operations, commodity type and prices and weather patterns, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Commercial non-real estate Small and middle market businesses and loans made to public sector Secured by business assets and guarantees of owners Cash flows Industry and geography of the borrower's business, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Residential real estate Residential mortgages and home equity loans and lines Secured by residential real estate Borrower's income Borrower's capacity and willingness to repay, unemployment rates and other economic factors, and customer repayment history Consumer and other Consumer loans and all other loan relationships that do not fit within categories above, including consumer and commercial credit cards and consumer deposit account overdrafts Secured by automobiles, unsecured 1 Residential real estate construction loans are included in the construction and development segment until construction is completed, after which the loan is moved to the residential real estate loan segment. Changes to the allowance for credit losses are made by charges to the provision for credit losses, which is reflected on the consolidated statements of income. Past due status is monitored as an indicator of credit deterioration. Loans deemed to be uncollectible are charged off against the allowance for credit losses. Recoveries of amounts previously charged-off are credited to the allowance for credit losses. Unfunded Commitments and Unfunded Commitments Reserve Unfunded residential mortgage loan commitments entered into in connection with mortgage loans to be held for sale are considered derivatives and are recorded at fair value and included in accrued expenses and other liabilities on the consolidated balance sheets with changes in fair value recorded in other interest income in the consolidated statements of income. All other unfunded loan commitments are generally related to providing credit facilities to customers and are not considered derivatives. The unfunded commitments reserve ("unfunded reserve") presents the expected credit losses on off-balance sheet commitments such as unfunded commitments to extend credit and standby letters of credit. An unfunded reserve is not recognized for commitments unconditionally cancellable by the Company, which includes credit cards, warehouse lines of credit and other revolving lines which are deemed to be unconditionally cancellable and is recorded in accrued expenses and other liabilities on the consolidated balance sheet. Changes to the unfunded reserve are recognized in provision for credit losses in the consolidated statements of income. The unfunded reserve is determined by estimating future draws and applying the expected loss rates on those draws. Future draws are based on historical averages of utilization rates (i.e., the likelihood of draws taken). Loss rates are estimated by utilizing the same loss rates calculated for the collective reserve of the allowance for credit losses. The Company's change in unfunded commitments reserve from the incurred loss methodology to the current expected credit loss methodology was immaterial as of the date of adoption and therefore no provision was recognized. Accrued Interest Receivable Upon adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, the Company has elected the following: • Accrued interest receivable balances are presented separately within the consolidated balance sheets, • Accrued interest receivable balances are excluded from amortized cost of financing receivables and related disclosure requirements, and • Uncollectible accrued interest receivable is written off by reversing interest income, generally upon becoming 90 days past due. Accordingly, we do not recognize an allowance for credit losses on accrued interest receivable. Subsequent Events The Company has evaluated all events or transactions that occurred through the date the Company issued these financial statements. Other than those described below, there were no material events or transactions that would require recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements.

New Accounting Standards

New Accounting Standards	3 Months Ended
	Dec. 31, 2020
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards	New Accounting Standards Accounting Standards Adopted in Fiscal Year 2021 In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, which address recording of estimated lifetime credit losses on loans, including funded and unfunded commitments, and other financial instruments held by financial institutions and other organizations. ASU 2016-13, as amended, requires institutions to measure all expected credit losses related to financial assets measured at amortized cost with an expected loss model based on historical experience, current conditions and reasonable and supportable forecasts relevant to affect the collectability of the financial assets, which is referred to as the CECL model. ASU 2016-13, as amended, requires enhanced disclosures, including qualitative and quantitative requirements, to help understand significant estimates and judgments used in estimating credit losses, as well as provide additional information about the amounts recorded in the financial statements. The measurement of expected losses under CECL is applicable to financial assets measured at amortized cost, including loan receivables and debt securities held to maturity. It also applies to off-balance sheet credit exposures not accounted for as insurance (loan commitments, standby letters of credit and other similar instruments). In addition, CECL requires debt securities available for sale with an unrealized loss to be recognized as allowance for credit loss rather than as a write-down of the securities amortized cost basis when management intends to sell or believes that it is not more-likely-than-not that they will be required to sell the securities prior to recovery of the securities amortized cost to be recognized as allowance for credit loss rather than as a write-down of the securities amortized cost basis . The CECL standard does not apply to the loan portfolio accounted for using the fair value option. The Company identified eight loan portfolio segments for which a model has been established to estimate credit losses. The historical data sets of these segments were identified, populated and validated. Each segment contains loans which have similar risk characteristics. Not unlike the incurred loss model, each segment is split into loans that are individually assessed and those that are collectively assessed. The Company adopted the standard on October 1, 2020, and applied the standard's provisions under the modified retrospective approach. Upon adoption of the standard, the Company recorded a $177.3 million increase to the ACL, of which $1.5 million related to the transfer of discounts on previously acquired loans and $175.8 million related to changes from the incurred loss model to the CECL model, which resulted in a cumulative effect adjustment decrease of $132.9 million (after-tax) to retained earnings. The tax effect resulted in a $42.9 million increase in deferred tax assets. In addition, the Company has elected the 5 year CECL transition for regulatory capital ratios, resulting in an add-back of $129.5 million to common equity tier 1 capital as of December 31, 2020. The following table presents the composition of loans and allowance by portfolio segment as of September 30, 2020, as adjusted at September 30, 2020 and October 1, 2020. Reported Balance September 30, Reclassifications ¹ Unamortized Discounts, Unearned Net Deferred Fees and Net Loans in Process Included in Amortized Cost ² Adjusted Balance September 30, Adoption of ASU 2016-13, as amended ³ Adjusted Balance October 1, 2020 (dollars in thousands) Loans: Construction and development n/a ⁴ $ 512,539 $ (2,895) $ 509,644 $ — $ 509,644 Owner-occupied CRE n/a ⁴ 1,420,061 (2,667) 1,417,394 36 1,417,430 Non-owner-occupied CRE n/a ⁴ 2,902,612 (8,232) 2,894,380 1,497 2,895,877 Multifamily residential real estate n/a ⁴ 536,828 (2,845) 533,983 (8) 533,975 Total commercial real estate 5,274,941 (5,274,941) — — — — Agriculture 1,724,350 — (1,654) 1,722,696 55 1,722,751 Commercial non-real estate 2,181,656 — (16,618) 2,165,038 (85) 2,164,953 Residential real estate 830,102 (97,099) (2,191) 730,812 23 730,835 Consumer and other — 100,553 1,642 102,195 (20) 102,175 Consumer 63,206 (63,206) — — — — Other 37,347 (37,347) — — — — Ending balance 10,111,602 — (35,460) 10,076,142 1,498 10,077,640 Less: Unamortized discount (8,215) — 8,215 — — — Unearned net deferred fees and (27,245) — 27,245 — — — Total $ 10,076,142 $ — $ — $ 10,076,142 $ 1,498 $ 10,077,640 Allowance: Construction and development n/a ⁴ $ (7,012) $ — $ (7,012) $ (11,963) $ (18,975) Owner-occupied CRE n/a ⁴ (20,530) — (20,530) (4,298) (24,828) Non-owner-occupied CRE n/a ⁴ (50,965) — (50,965) (98,986) (149,951) Multifamily residential real estate n/a ⁴ (6,726) — (6,726) (2,681) (9,407) Total commercial real estate (84,496) 84,496 — — — — Agriculture (27,018) — — (27,018) (24,360) (51,378) Commercial non-real estate (27,599) — — (27,599) (32,938) (60,537) Residential real estate (8,202) 737 — (7,465) (2,595) (10,060) Consumer and other (2,572) — — (2,572) 532 (2,040) Total $ (149,887) $ — $ — $ (149,887) $ (177,289) $ (327,176) 1 Reclassifications made from reported loan and related allowance segments to align with the eight loan portfolio segments established for adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, to estimate credit losses. 2 Unamortized discount on acquired loans, unearned net deferred fees and costs and net loans in process to related were assigned to appropriate loan portfolio segment to present loan categories at amortized cost. 3 Discounts on previously acquired loans and Day 1 impact of adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, were transferred to allowance for credit losses as a part of CECL adoption. 4 Balance for this segment is included in total commercial real estate for September 30, 2020. The Company did not record an allowance for available for sale or held to maturity securities upon adoption as the investment portfolio consisted primarily of debt securities explicitly or implicitly backed by the U.S. Government for which expected credit loss is zero. We adopted the CECL standard using the prospective transition approach for financial assets purchased with credit deterioration ("PCD") that were previously classified as purchased credit impaired ("PCI") and accounted for under ASC 310-30. In accordance with the standard, we did not reassess whether PCI assets met the definition of PCD assets as of the date of adoption. On October 1, 2020, the Company determined $1.5 million of existing discounts on PCD loans was related to credit factors and was reclassified to the ACL. The remaining noncredit discount of $6.7 million was determined to be related to noncredit factors and will be accreted into interest income on a level-yield method over the remaining life of the loans. For additional information, see "Note 1. Nature of Operations and Summary of Significant Policies", "Note 3. Securities Available for Sale", and "Note 4. Loans and Allowance for Credit Losses." Accounting Standards Not Yet Adopted in Fiscal Year 2021 In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes in the Disclosure Requirements for Fair Value Measurement , which eliminates, adds 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. ASU 2018-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. Entities are also allowed to elect to early adopt the eliminated or modified disclosure requirements and delay adoption of the new disclosure requirements until after their effective date. As ASU 2018-13 only revises disclosure requirements, the Company does not believe this ASU will have a material impact on the consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , which aims to simplify the accounting for income taxes by removing certain exceptions to the general principles and also simplification of areas such as franchise taxes, step-up in tax basis goodwill, separate entity financial statements and interim recognition of enactment of tax laws or rate changes. The ASU will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating the potential impact of ASU 2019-12 on the consolidated financial statements. In January 2020, the FASB issued ASU 2020-01, Investments - Equity Securities (Topic 321), Investments - Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815): Clarifying the Interactions between Topic 321, Topic 323 and Topic 815 , which clarifies that an entity should consider observable transactions that require it to either apply or discontinue the equity method of accounting for the purposes of applying the fair value measurement alternative. The ASU will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company does not expect adoption to have a material impact on the consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting , which provides optional expedients and exceptions for a limited time period to ease the potential burden in accounting for reference rate reform on financial reporting. The amendments in ASU 2020-04 are elective for entities with contracts, including derivative contracts, that reference LIBOR or some other reference rate that are expected to be discontinued. For the Company's cash flow hedges, ASU 2020-04 allows: (i) an entity to change the reference rate without having to designate the hedging relationship; (ii) for cash flow hedges in which the designated hedged risk is LIBOR, allows an entity to assert that it remains probable that the hedged forecasted transaction will occur; and (iii) allows an entity to change the designated method used to assess hedge effectiveness and simplifies or temporarily suspends the assessment of hedge effectiveness for hedging relationships. ASU 2020-04 must be applied prospectively and was effective immediately upon issuance and remains effective through December 31, 2022. The Company is currently evaluating the impact that adopting this new accounting standard will have on the consolidated financial statements.

Securities Available for Sale

Securities Available for Sale	3 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Securities Available for Sale	Securities Available for Sale The amortized cost and approximate fair value of investments in securities, all of which are classified as available for sale according to management’s intent, are summarized as follows. Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated (dollars in thousands) As of December 31, 2020 U.S. Treasury securities $ 24,991 $ 23 $ — $ 25,014 U.S. Agency securities 24,975 — (272) 24,703 Mortgage-backed securities: Government National Mortgage Association 424,756 10,220 (102) 434,874 Federal Home Loan Mortgage Corporation 769,254 17,187 (65) 786,376 Federal National Mortgage Association 455,651 7,301 (206) 462,746 Small Business Assistance Program 264,798 7,829 (192) 272,435 States and political subdivision securities 51,120 1,297 — 52,417 Other 1,006 44 — 1,050 Total $ 2,016,551 $ 43,901 $ (837) $ 2,059,615 Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated (dollars in thousands) As of September 30, 2020 U.S. Treasury securities $ 49,924 $ 228 $ — $ 50,152 U.S. Agency securities 24,974 86 — 25,060 Mortgage-backed securities: Government National Mortgage Association 485,689 11,481 (43) 497,127 Federal Home Loan Mortgage Corporation 578,650 18,919 (9) 597,560 Federal National Mortgage Association 287,842 7,788 (16) 295,614 Small Business Assistance Program 244,653 7,884 (58) 252,479 States and political subdivision securities 54,224 1,356 — 55,580 Other 1,006 48 — 1,054 Total $ 1,726,962 $ 47,790 $ (126) $ 1,774,626 The amortized cost and approximate fair value of debt securities available for sale as of December 31, 2020 and September 30, 2020, by contractual maturity, are shown below. Maturities of mortgage-backed securities may differ from contractual maturities because the mortgages underlying the securities may be called or repaid without penalty. December 31, 2020 September 30, 2020 Amortized Estimated Amortized Estimated (dollars in thousands) Due in one year or less $ 42,973 $ 43,103 $ 67,131 $ 67,456 Due after one year through five years 48,047 48,499 51,779 52,694 Due after five years through ten years 10,066 10,532 10,212 10,642 Due after ten years — — — — 101,086 102,134 129,122 130,792 Mortgage-backed securities 1,914,459 1,956,431 1,596,834 1,642,780 Securities without contractual maturities 1,006 1,050 1,006 1,054 Total $ 2,016,551 $ 2,059,615 $ 1,726,962 $ 1,774,626 There were no sales of securities available for sale for both the three months ended December 31, 2020 and 2019 and as such there were no proceeds from the sales of securities available for sale for same periods. No gross gains (pre-tax) were realized on the sales for each of the three months ended December 31, 2020 and 2019, using the specific identification method. No gross losses (pre-tax) were realized on the sales for each of the three months ended December 31, 2020 and 2019, using the specific identification method. Securities with an estimated fair value of approximately $1.07 billion and $1.10 billion at December 31, 2020 and September 30, 2020, respectively, were pledged as collateral on public deposits, securities sold under agreements to repurchase, and for other purposes as required by contractual obligation or law. The counterparties do not have the right to sell or pledge the securities the Company has pledged as collateral. As detailed in the following tables, certain investments in debt securities, which are approximately 9% and 6% of the Company’s investment portfolio at estimated fair value at December 31, 2020 and September 30, 2020, respectively, are reported in the consolidated financial statements at an amount less than their amortized cost. Based on evaluation of available evidence, including recent changes in market interest rates, credit rating information, implicit or explicit government guarantees, and information obtained from regulatory filings, management believes the declines in fair value of these securities are not the result of credit losses at December 31, 2020, and therefore, an allowance for credit losses was not recorded. Prior to the adoption of ASU 2016-13, as amended, the Company recognized no other-than-temporary impairment for the three months ended December 31, 2019. The following table presents the Company’s gross unrealized losses and approximate fair value in investments, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position. Less than 12 months 12 months or more Total Estimated Unrealized Estimated Unrealized Estimated Unrealized (dollars in thousands) As of December 31, 2020 U.S. Agency securities $ 24,703 $ (272) $ — $ — $ 24,703 $ (272) Mortgage-backed securities 146,799 (553) 8,388 (12) 155,187 (565) Total $ 171,502 $ (825) $ 8,388 $ (12) $ 179,890 $ (837) Less than 12 months 12 months or more Total Estimated Unrealized Estimated Unrealized Estimated Unrealized (dollars in thousands) As of September 30, 2020 U.S. Agency securities $ — $ — $ — $ — $ — $ — Mortgage-backed securities 71,547 (103) 27,897 (23) 99,444 (126) Total $ 71,547 $ (103) $ 27,897 $ (23) $ 99,444 $ (126) As of December 31, 2020 and September 30, 2020, the Company had 22 and 18 securities, respectively, in an unrealized loss position.

Loans and Allowance for Credit

Loans and Allowance for Credit Losses	3 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Loans and Allowance for Credit Losses	Loans and Allowance for Credit Losses The following table presents the composition of loans at amortized cost as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 Total Loans Less: Fair Value Option Loans Less: Guaranteed Loans ¹ Loans at Amortized Cost Total Loans ² Less: Fair Value Option Loans Less: Guaranteed Loans ¹ Loans at Amortized Cost (dollars in thousands) Construction and development $ 482,462 $ — $ — $ 482,462 $ 509,644 $ — $ — $ 509,644 Owner-occupied CRE 1,411,558 107,541 47,808 1,256,209 1,417,394 109,097 48,468 1,259,829 Non-owner-occupied CRE 2,660,682 260,916 27,168 2,372,598 2,894,380 283,266 27,402 2,583,712 Multifamily residential real estate 476,159 3,045 — 473,114 533,983 3,847 — 530,136 Total commercial real estate 5,030,861 371,502 74,976 4,584,383 5,355,401 396,210 75,870 4,883,321 Agriculture 1,635,952 115,925 39,426 1,480,601 1,722,696 129,041 42,353 1,551,302 Commercial non-real estate 2,054,478 124,161 715,163 1,215,154 2,165,038 129,934 744,371 1,290,733 Residential real estate ³ 708,086 — 294 707,792 730,812 — 290 730,522 Consumer and other ⁴ 88,499 — — 88,499 102,195 — 102,195 Total $ 9,517,876 $ 611,588 $ 829,859 $ 8,076,429 $ 10,076,142 $ 655,185 $ 862,884 $ 8,558,073 1 Includes loans guaranteed by agencies of the U.S. government. 2 As a part of the adoption of CECL, loan segments are presented based on amortized cost, which includes unpaid principal balance, unamortized discount on acquired loans, and unearned net deferred fees and costs. For additional information on September 30, 2020 loan segment balances, see Note 2. 3 Includes residential real estate loans held for sale of $11.6 million and $12.4 million at December 31, 2020 and September 30, 2020, respectively, recorded at the lower of cost or fair value.. 4 Other loans primarily include consumer and commercial credit cards, customer deposit account overdrafts and loans in process. The following table presents the Company’s past due and nonaccrual loans at amortized cost as of December 31, 2020. This table excludes loans measured at fair value under the fair value option of $611.6 million at December 31, 2020. Loans greater than 90 days past due and still accruing interest as of December 31, 2020 were nominal. As of December 31, 2020 Current or Less Than 30 Days Past Due 30-89 Days Past Due Nonaccrual Total (dollars in thousands) Construction and development $ 468,025 $ 180 $ 14,257 $ 482,462 Owner-occupied CRE 1,286,830 411 16,776 1,304,017 Non-owner-occupied CRE 2,346,904 16,097 36,765 2,399,766 Multifamily residential real estate 472,675 439 — 473,114 Total commercial real estate 4,574,434 17,127 67,798 4,659,359 Agriculture 1,322,075 12,319 185,633 1,520,027 Commercial non-real estate 1,909,610 3,210 17,497 1,930,317 Residential real estate 698,146 3,166 6,774 708,086 Consumer and other 88,228 152 70 88,450 Total $ 8,592,493 $ 35,974 $ 277,772 $ 8,906,239 The following table presents the Company’s past due loans at September 30, 2020. This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value under the fair value option of $655.2 million at September 30, 2020. Current or Less Than 30 Days Past Due 30-89 Days Past Due Nonaccrual Total (dollars in thousands) As of September 30, 2020 Commercial real estate $ 4,790,963 $ 8,894 $ 73,146 $ 4,873,003 Agriculture 1,317,377 60,020 217,642 1,595,039 Commercial non-real estate 2,021,308 3,512 26,843 2,051,663 Residential real estate 821,154 2,459 4,441 828,054 Consumer and other 100,319 45 74 100,438 Ending balance $ 9,051,121 $ 74,930 $ 322,146 $ 9,448,197 The following table provides additional information on nonaccrual loans for the three months ended December 31, 2020. There were no loans greater than 90 days past due and still accruing interest as of September 30, 2020. Three Months Ended December 31, 2020 Nonaccrual Nonaccrual Nonaccrual Loans with No Related ACL Interest Income Recognized on Nonaccrual Loans Accrued Interest Written Off on Nonaccrual Loans (dollars in thousands) Construction and development n/a ¹ $ 14,257 $ — $ — $ 110 Owner-occupied CRE n/a ¹ 16,776 8,036 — 13 Non-owner-occupied CRE n/a ¹ 36,765 11,686 — 1,717 Multifamily residential real estate n/a ¹ — — — — Total commercial real estate $ 73,146 67,798 19,722 — 1,840 Agriculture 217,642 185,633 154,508 — 382 Commercial non-real estate 26,843 17,497 7,711 — 2 Residential real estate 4,441 6,774 — — 25 Consumer and other 74 70 — — 1 Total $ 322,146 $ 277,772 $ 181,941 $ — $ 2,250 1 Balance for this segment is included in total commercial real estate for September 30, 2020. This table presents the loans based on credit quality, loan segment and year of origination at amortized cost and excludes loans measured at fair value under the fair value option of $611.6 million at December 31, 2020. Term loans Fiscal Year to Date Fiscal Year 2021 2020 2019 2018 2017 Prior to 2017 Revolving Loans Revolving Loans Total (dollars in thousands) Construction and development Pass $ 86,339 $ 160,884 $ 108,053 $ 30,830 $ 2,570 $ 824 $ 63,584 $ — $ 453,084 Special Mention 3,686 — 200 — — — — — 3,886 Substandard 11,322 33 — 12,746 — — 1,364 — 25,465 Doubtful — — 27 — — — — — 27 Total construction and development $ 101,347 $ 160,917 $ 108,280 $ 43,576 $ 2,570 $ 824 $ 64,948 $ — $ 482,462 Owner-occupied CRE Pass $ 104,322 $ 372,920 $ 227,194 $ 117,287 $ 164,280 $ 185,366 $ 51,397 $ 59 $ 1,222,825 Special Mention 465 1,853 2,170 6,651 8,481 8,032 332 — 27,984 Substandard 4,358 4,609 4,643 18,257 11,704 6,447 — — 50,018 Doubtful — — 3,190 — — — — — 3,190 Total owner-occupied CRE $ 109,145 $ 379,382 $ 237,197 $ 142,195 $ 184,465 $ 199,845 $ 51,729 $ 59 $ 1,304,017 Non-owner-occupied CRE Pass $ 161,105 $ 423,025 $ 360,220 $ 348,757 $ 382,487 $ 334,667 $ 44,898 $ — $ 2,055,159 Special Mention 18,991 1,555 35,322 77,164 15,448 16,874 — — 165,354 Substandard 14,418 64,261 15,527 41,830 — 7,758 35,459 — 179,253 Doubtful — — — — — — — — — Total non-owner-occupied CRE $ 194,514 $ 488,841 $ 411,069 $ 467,751 $ 397,935 $ 359,299 $ 80,357 $ — $ 2,399,766 Multifamily residential real estate Pass $ 72,043 $ 100,793 $ 102,328 $ 71,541 $ 16,889 $ 56,216 $ 248 $ — $ 420,058 Special Mention 256 — 2,629 20,686 46 107 21,200 — 44,924 Substandard — 7,311 — — 487 334 — — 8,132 Doubtful — — — — — — — — — Total multifamily residential real estate $ 72,299 $ 108,104 $ 104,957 $ 92,227 $ 17,422 $ 56,657 $ 21,448 $ — $ 473,114 Total commercial real estate Pass $ 423,809 $ 1,057,622 $ 797,795 $ 568,415 $ 566,226 $ 577,073 $ 160,127 $ 59 $ 4,151,126 Special Mention 23,398 3,408 40,321 104,501 23,975 25,013 21,532 — 242,148 Substandard 30,098 76,214 20,170 72,833 12,191 14,539 36,823 — 262,868 Doubtful — — 3,217 — — — — — 3,217 Total commercial real estate $ 477,305 $ 1,137,244 $ 861,503 $ 745,749 $ 602,392 $ 616,625 $ 218,482 $ 59 $ 4,659,359 Term loans Fiscal Year to Date Fiscal Year 2021 2020 2019 2018 2017 Prior to 2017 Revolving Loans Revolving Loans Total (dollars in thousands) Agriculture Pass $ 56,160 $ 222,029 $ 105,591 $ 85,249 $ 82,726 $ 62,253 $ 460,060 $ — $ 1,074,068 Special Mention 21,040 29,166 7,402 13,400 23,817 4,511 49,451 — 148,787 Substandard 11,412 36,842 15,034 41,653 39,723 8,121 114,838 — 267,623 Doubtful 1,595 49 754 22,230 1,446 — 3,475 — 29,549 Total agriculture $ 90,207 $ 288,086 $ 128,781 $ 162,532 $ 147,712 $ 74,885 $ 627,824 $ — $ 1,520,027 Commercial non-real estate Pass $ 28,084 $ 827,457 $ 195,666 $ 63,526 $ 52,661 $ 43,956 $ 573,735 $ 8 $ 1,785,093 Special Mention 6,500 21,521 2,812 1,714 2,576 864 19,391 — 55,378 Substandard 7,950 20,120 12,992 4,561 255 1,395 32,619 — 79,892 Doubtful — 390 52 84 — 4,269 5,159 — 9,954 Total commercial non-real estate $ 42,534 $ 869,488 $ 211,522 $ 69,885 $ 55,492 $ 50,484 $ 630,904 $ 8 $ 1,930,317 Residential real estate ¹ Pass $ 48,697 $ 213,698 $ 86,203 $ 52,442 $ 31,231 $ 119,770 $ 138,017 $ 282 $ 690,340 Special Mention 297 825 341 303 304 998 220 — 3,288 Substandard 279 1,545 2,828 1,363 421 6,083 1,937 — 14,456 Doubtful — — — — — 2 — — 2 Total residential real estate $ 49,273 $ 216,068 $ 89,372 $ 54,108 $ 31,956 $ 126,853 $ 140,174 $ 282 $ 708,086 Consumer and other ¹ Pass $ 31,451 $ 22,536 $ 16,856 $ 2,898 $ 1,220 $ 1,370 $ 12,058 $ — $ 88,389 Special Mention 9 — — — — 12 3 — 24 Substandard 6 6 18 2 10 8 35 — 85 Doubtful — — — 1 — — — — 1 Total consumer and other $ 31,466 $ 22,542 $ 16,874 $ 2,901 $ 1,230 $ 1,390 $ 12,096 $ — $ 88,499 Total loans Pass $ 588,201 $ 2,343,342 $ 1,202,111 $ 772,530 $ 734,064 $ 804,422 $ 1,343,997 $ 349 $ 7,789,016 Special Mention 51,244 54,920 50,876 119,918 50,672 31,398 90,597 — 449,625 Substandard 49,745 134,727 51,042 120,412 52,600 30,146 186,252 — 624,924 Doubtful 1,595 439 4,023 22,315 1,446 4,271 8,634 — 42,723 Total loans $ 690,785 $ 2,533,428 $ 1,308,052 $ 1,035,175 $ 838,782 $ 870,237 $ 1,629,480 $ 349 $ 8,906,288 1 The Company generally does not risk rate residential real estate or consumer and other loans unless a default event such as a bankruptcy or extended nonperformance takes place. Alternatively, standard credit scoring systems are used to assess credit risks of residential real estate and consumer and other loans. The following table presents the composition of the loan portfolio by internally assigned grade as of September 30, 2020. This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value under the fair value option of $655.2 million at September 30, 2020. As of September 30, 2020 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer and Other ¹ Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,062,814 $ 968,875 $ 1,851,323 $ 806,436 $ 99,632 $ 7,789,080 Watchlist 577,399 265,714 94,401 6,972 709 945,195 Substandard 229,467 348,910 94,316 13,173 93 685,959 Doubtful 3,323 11,540 11,623 1,473 4 27,963 Loss — — — — — — Ending balance 4,873,003 1,595,039 2,051,663 828,054 100,438 9,448,197 1 The Company generally does not risk rate residential real estate or consumer and other loans unless a default event such as a bankruptcy or extended nonperformance takes place. Alternatively, standard credit scoring systems are used to assess credit risks of residential real estate and consumer and other loans. Additional disclosures previously required by ASC Topic 310 related to the Company's September 30, 2020 balances and activity for the quarter ended December 31, 2019 are included as follows: The following table presents the Company’s impaired loans at September 30, 2020. This table excludes purchased credit impaired loans and loans measured at fair value under the fair value option. September 30, 2020 Recorded Investment Unpaid Principal Balance Related Allowance for Credit Losses Impaired loans: (dollars in thousands) With an allowance for credit losses recorded: Commercial real estate $ 111,121 $ 114,034 $ 25,087 Agriculture 53,052 55,145 8,151 Commercial non-real estate 39,821 47,571 7,822 Residential real estate 5,670 6,314 1,903 Consumer and other 98 109 30 Total impaired loans with an allowance for credit losses recorded 209,762 223,173 42,993 With no allowance for credit losses recorded: Commercial real estate 121,380 161,211 — Agriculture 308,734 332,272 — Commercial non-real estate 66,542 75,365 — Residential real estate 6,543 8,818 — Consumer and other — 108 — Total impaired loans with no allowance for credit losses recorded 503,199 577,774 — Total impaired loans $ 712,961 $ 800,947 $ 42,993 The following table presents the average recorded investment on impaired loans and interest income recognized on impaired loans for the three months ended December 31, 2019. Three Months Ended December 31, 2019 Average Recorded Investment Interest Income Recognized While on Impaired Status (dollars in thousands) Commercial real estate $ 73,422 $ 2,379 Agriculture 360,397 8,517 Commercial non-real estate 72,389 2,870 Residential real estate 9,013 266 Consumer 179 1 Total $ 515,400 $ 14,033 The Company did not acquire any loans during the three months ended December 31, 2020. Prior to October 1, 2020, the Company accounted for acquired impaired loans in accordance with ASC 310-30. The following is a summary of changes in the accretable difference for all loans accounted for under ASC 310-30 during the three months ended December 31, 2019. Three Months Ended December 31, 2019 (dollars in thousands) Balance, beginning of period $ 26,047 Accretion (1,940) Reclassification (to) from nonaccretable difference (2,977) Balance, end of period $ 21,130 Troubled Debt Restructurings Included in certain loan categories in the impaired loans are TDRs that were classified as impaired. Loans are designated as TDRs when the borrower is experiencing financial difficulty, and the Company agrees to concessions that are both significant and outside of market terms. Individual reserves included in the allowance for credit losses for TDRs were $8.5 million and $11.0 million at December 31, 2020 and September 30, 2020, respectively. There were no commitments to lend additional funds to borrowers whose loans were modified in a TDR at both December 31, 2020 and September 30, 2020. The following table presents the amortized cost of the Company’s TDR balances as of December 31, 2020 and recorded value of TDR balances as of September 30, 2020. December 31, 2020 September 30, 2020 Accruing Nonaccrual Accruing Nonaccrual (dollars in thousands) Construction and development $ 1,364 $ 27 n/a ¹ n/a ¹ Owner-occupied CRE 5,590 — n/a ¹ n/a ¹ Non-owner-occupied CRE 12,203 11,637 n/a ¹ n/a ¹ Multifamily residential real estate — — n/a ¹ n/a ¹ Total commercial real estate 19,157 11,664 $ 23,215 $ 11,913 Agriculture 3,356 35,736 2,976 45,971 Commercial non real estate 8,304 5,096 8,734 4,803 Real estate 269 69 277 74 Consumer and other 2 27 3 31 Total $ 31,088 $ 52,592 $ 35,205 $ 62,792 1 Balance for this segment is included in total commercial real estate for September 30, 2020. TDRs are generally restructured through either a rate modification, term extension, payment modification or due to a bankruptcy. The following table presents a summary of all accruing loans restructured in TDRs for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Construction and development — $ — $ — n/a ¹ n/a ¹ n/a ¹ Owner-occupied CRE — — — n/a ¹ n/a ¹ n/a ¹ Non-owner-occupied CRE 1 10,640 10,640 n/a ¹ n/a ¹ n/a ¹ Multifamily residential real estate — — — n/a ¹ n/a ¹ n/a ¹ Total commercial real estate 1 10,640 10,640 — — — Agriculture 1 700 700 — — — Commercial non-real estate — — — 2 1,144 1,444 Residential real estate — — — — — — Consumer and other — — — — — — Total accruing 2 $ 11,340 $ 11,340 2 $ 1,144 $ 1,444 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — 1 Balance for this segment is included in total commercial real estate for September 30, 2020. The following table presents a summary of all nonaccruing loans restructured in TDRs for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Construction and development — $ — $ — n/a ¹ n/a ¹ n/a ¹ Owner-occupied CRE — — — n/a ¹ n/a ¹ n/a ¹ Non-owner-occupied CRE — — — n/a ¹ n/a ¹ n/a ¹ Multifamily residential real estate — — — n/a ¹ n/a ¹ n/a ¹ Total commercial real estate — — — 1 2,216 2,216 Agriculture 3 2,776 2,776 10 1,455 1,455 Commercial non-real estate 1 748 748 2 830 830 Residential real estate — — — — — — Consumer and other — — — — — — Total nonaccruing 4 $ 3,524 $ 3,524 13 $ 4,501 $ 4,501 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — 1 Balance for this segment is included in total commercial real estate for September 30, 2020. The following table presents loans that were modified as TDRs within the previous 12 months and for which there was a payment default or a charge-off for the three months ended December 31, 2020 and 2019, respectively. Three Months Ended December 31, 2020 2019 Number of Loans Recorded Investment Number of Loans Recorded Investment (dollars in thousands) Construction and development — $ — n/a ¹ n/a ¹ Owner-occupied CRE — — n/a ¹ n/a ¹ Non-owner-occupied CRE — — n/a ¹ n/a ¹ Multifamily residential real estate — — n/a ¹ n/a ¹ Total commercial real estate — — — $ — Agriculture — — 19 14,347 Commercial non-real estate 3 653 1 2,834 Residential real estate — — — — Consumer and other — — — — Total 3 $ 653 20 $ 17,181 1 Balance for this segment is included in total commercial real estate for September 30, 2020. For purposes of the table above, a loan is considered to be in payment default once it is 90 days or more contractually past due under the modified terms. The table includes loans that experienced a payment default during the period, but may be performing in accordance with the modified terms as of the balance sheet date. During the three months ended December 31, 2020 and 2019, there were no loans removed from TDR status as they were restructured at market terms and are performing. Allowance for Credit Losses ("ACL") As previously mentioned in Note 2. New Accounting Standards, the Company adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, and subsequent related ASUs, which resulted in a significant change to the Company's methodology for estimating the ACL. As a result of this adoption, the Company recorded a $177.3 million increase to the allowance as a cumulative-effect adjustment on October 1, 2020. The following tables presents ACL activity by loan portfolio segment for the three months ended December 31, 2020. Three Months Ended December 31, 2020 Adjusted balance September 30, 2020 ¹ Adoption of ASU 2016-13, as amended Adjusted beginning balance, October 1, 2020 Charge-offs Recoveries (Reversal of) provision for credit losses on loans Ending balance, December 31, 2020 (dollars in thousands) Construction and development $ 7,012 $ 11,963 $ 18,975 $ (27) $ 268 $ (502) $ 18,714 Owner-occupied CRE 20,530 4,298 24,828 — — 258 25,086 Non-owner-occupied CRE 50,965 98,986 149,951 (28,269) 61 (992) 120,751 Multifamily residential real estate 6,726 2,681 9,407 — — 366 9,773 Total commercial real estate 85,233 117,928 203,161 (28,296) 329 (870) 174,324 Agriculture 27,018 24,360 51,378 (2,144) 1,734 (3,989) 46,979 Commercial non-real estate 27,599 32,938 60,537 (2,043) 245 17,216 75,955 Residential real estate 7,465 2,595 10,060 (96) 32 (324) 9,672 Consumer and other 2,572 (532) 2,040 (232) 113 (57) 1,864 Total $ 149,887 $ 177,289 $ 327,176 $ (32,811) $ 2,453 $ 11,976 $ 308,794 1 At September 30, 2020, the allowance balances were reclassified to align with the eight loan portfolio segments established for adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs. For additional information, see Note 2. The allowance for unfunded commitments was $2.3 million and $2.4 million at December 31, 2020 and September 30, 2020, respectively, and is recorded in accrued expenses and other liabilities on the consolidated balance sheets. The (reversal of) provision for unfunded commitments was $0.1 million for the three months ended December 31, 2020 and is included in provision for credit losses in the consolidated statements of income. The provision for unfunded commitments was $0.2 million for the three months ended December 31, 2019 and is included in other noninterest expense in the consolidated statements of income. The following table presents ACL activity by loan portfolio segment for the three months ended December 31, 2019. Three Months Ended December 31, 2019 Beginning balance, October 1, 2019 Charge-offs Recoveries Provision for credit losses on loans Impairment (improvement) of ASC 310-30 loans Ending balance, December 31, 2019 (dollars in thousands) Commercial real estate $ 16,827 $ (37) $ 120 $ 572 $ (20) $ 17,462 Agriculture 30,819 (4,606) 103 5,978 (265) 32,029 Commercial non-real estate 17,567 (1,481) 112 1,191 — 17,389 Residential real estate 4,095 (169) 164 192 338 4,620 Consumer and other 1,466 (373) 71 117 — 1,281 Total $ 70,774 $ (6,666) $ 570 $ 8,050 $ 53 $ 72,781

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial InstrumentsThe Company uses interest rate swaps and interest rate caps/floors to manage its interest rate risk and market risk in accommodating the needs of its customers. Interest rate swaps include both traditional interest rate swaps and interest rate swaps which can be canceled by the customer on specified dates at no cost, typically referred to as swaptions. The Company recognizes all derivatives on the consolidated balance sheet at fair value in either other assets or accrued expenses and other liabilities as appropriate. The following table presents the notional amounts and gross fair values of all derivative assets and liabilities held by the Company as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 Notional Amount Gross Asset Gross Liability Notional Amount Gross Asset Gross Liability (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps - FVO loan portfolio Financial institution counterparties $ 562,359 $ — $ (54,568) $ 592,241 $ — $ (62,587) Interest rate swaps - Other Financial institution counterparties 708,872 — (1,516) 641,189 — (1,672) Customer counterparties 708,872 74,495 — 641,189 83,533 — Interest rate caps Financial institution counterparties 26,538 2 — 20,538 2 — Customer counterparties 26,538 — (2) 20,538 — (2) Risk participation agreements 82,111 — (22) 80,681 — (32) Mortgage loan commitments 79,738 322 — 92,278 — (96) Mortgage loan forward sale contracts 80,441 — (322) 94,084 96 — Total $ 2,275,469 $ 74,819 $ (56,430) $ 2,182,738 $ 83,631 $ (64,389) Netting of Derivatives The Company records the derivatives on a net basis when a right of offset exists, based on transactions with a single counterparty that are subject to a legally enforceable master netting agreement. When bilateral netting agreements or similar agreements exist between the Company and its counterparties that create a single legal claim or obligation to pay or receive the net amount in settlement of the individual derivative contracts, the Company reports derivative assets and liabilities on a net by derivative contract by counterparty basis. The following tables provide information on the Company's netting adjustments as of December 31, 2020 and September 30, 2020. Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of December 31, 2020 Total Derivative Assets $ 74,819 $ (4,321) $ 17,763 $ 88,261 Total Derivative Liabilities ¹ (56,430) 4,321 51,785 (324) 1 There was an additional $25.1 million of collateral held for initial margin with a Futures Clearing Merchant for clearing derivatives at December 31, 2020 and is included in other assets in the consolidated balance sheets. Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of September 30, 2020 Total Derivative Assets $ 83,631 $ (5,263) $ 20,012 $ 98,380 Total Derivative Liabilities ¹ (64,389) 5,263 59,028 (98) 1 There was an additional $22.9 million of collateral held for initial margin with a Futures Clearing Merchant for clearing derivatives at September 30, 2020 and is included in other assets in the consolidated balance sheets. As with any financial instrument, derivative financial instruments have inherent risk including adverse changes in interest rates. The Company’s exposure to derivative credit risk is defined as the possibility of sustaining a loss due to the failure of the counterparty to perform in accordance with the terms of the contract. Credit risks associated with interest rate swaps are similar to those relating to traditional on-balance sheet financial instruments. The Company manages interest rate swap credit risk with the same standards and procedures applied to its commercial lending activities. Credit-risk-related contingent features The Company has agreements with its derivative counterparties that contain a provision where if the Company or the derivative counterparty fails to maintain its status as a well/adequately capitalized institution, then the other party has the right to terminate the derivative positions and the Company or the derivative counterparty would be required to settle its obligations under the agreements. The Company has minimum collateral pledging thresholds with its Swap Dealers and Futures Clearing Merchant. The Company enters into RPAs with some of its derivative counterparties to assume the credit exposure related to interest rate derivative contracts. The Company's loan customer enters into an interest rate swap directly with a derivative counterparty and the Company agrees through an RPA to take on the counterparty's risk of loss on the interest rate swap due to a default by the customer. The effect of derivatives on the consolidated statements of income for the three months ended December 31, 2020 and 2019 was as follows. Amount of (Loss) Gain Recognized in Consolidated Statements of Income Three Months Ended December 31, Location of (Loss) Gain Recognized in Consolidated Statements of Income 2020 2019 (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps - FVO loan portfolio Derivative interest expense $ (3,393) $ (890) Interest rate swaps - FVO loan portfolio Change in fair value of FVO loans and related derivatives 8,570 12,809 Interest rate swaps and other derivatives Other derivative income 898 1,597 Mortgage loan commitments Other derivative income (418) 28 Mortgage loan forward sale contracts Other derivative income 418 (28)

The Fair Value Option for Certa

The Fair Value Option for Certain Loans	3 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
The Fair Value Option For Certain Loans	The Fair Value Option for Certain Loans The Company has elected to measure certain long-term loans at fair value to assist in managing the interest rate risk for longer-term loans. This fair value option was elected upon the origination of these loans. Interest income is recognized in the same manner as interest on non-fair value loans. See Note 14 for additional disclosures regarding the fair value of the fair value option loans. Long-term loans for which the fair value option has been elected had a net favorable difference between the aggregate fair value and the aggregate unpaid loan principal balance and written loan commitment amount of approximately $31.6 million at December 31, 2020 and a net favorable difference of approximately $37.3 million at September 30, 2020. The total unpaid principal balance of these long-term loans was approximately $580.0 million and $617.9 million at December 31, 2020 and September 30, 2020, respectively. The fair value of these loans is included in total loans in the consolidated balance sheets and are grouped with commercial real estate, agricultural and commercial non-real estate loans in Note 4. As of December 31, 2020 and September 30, 2020, there were loans with a fair value of $14.6 million and $21.7 million, respectively, which were greater than 90 days past due or in nonaccrual status with an unpaid principal balance of $14.6 million and $26.2 million, respectively. Changes in fair value for items for which the fair value option has been elected were a decrease in fair value of $10.2 million and $14.9 million for the three months ended December 31, 2020 and December 31, 2019, respectively. These changes in fair value are reported net of the related derivative activity in change in fair value of FVO loans and related derivatives within the consolidated statements of income. For long-term loans, $1.5 million and $2.1 million for the three months ended December 31, 2020 and December 31, 2019, respectively, of the total change in fair value is attributable to changes in specific credit risk. The gains or losses attributable to changes in instrument-specific credit risk were determined based on an assessment of existing market conditions and credit quality of the underlying loan for the specific portfolio of loans.

Core Deposits and Other Intangi

Core Deposits and Other Intangibles	3 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Core Deposits and Other Intangibles	Core Deposits and Other Intangibles The following table presents a summary of intangible assets subject to amortization as of December 31, 2020 and September 30, 2020. Core Deposit Intangible Customer Relationships Intangible Other Total (dollars in thousands) As of December 31, 2020 Gross carrying amount $ 7,339 $ 3,172 $ 538 $ 11,049 Accumulated amortization (4,499) (305) (341) (5,145) Net intangible assets $ 2,840 $ 2,867 $ 197 $ 5,904 As of September 30, 2020 Gross carrying amount $ 7,339 $ 3,172 $ 538 $ 11,049 Accumulated amortization (4,316) (244) (325) (4,885) Net intangible assets $ 3,023 $ 2,928 $ 213 $ 6,164 Amortization expense of intangible assets were $0.3 million and $0.4 million for the three months ended December 31, 2020 and December 31, 2019, respectively. The estimated amortization expense of intangible assets assumes no activities, such as acquisitions, which would result in additional amortizable intangible assets. Estimated amortization expense of intangible assets in subsequent fiscal years is as follows. Fiscal year Amount (dollars in thousands) Remaining in 2021 $ 754 2022 929 2023 831 2024 742 2025 683 2026 and thereafter 1,965 Total $ 5,904

Leases

Leases	3 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	Leases ASC Topic 842, Leases ("ASC 842"), became effective for the Company on October 1, 2019. ASC 842 requires a lease, whether classified as an operating lease or a financing lease, be accounted for as a right-of-use asset ("ROU asset") with a related lease liability recorded at the present value of the lease payments. The ROU asset represents the Company's right to use an underlying asset for the lease term and is included in other assets Subsequent to the adoption of ASC 842, the Company assesses contracts at inception to determine whether the contract is a lease or contains an embedded lease. A ROU asset and lease liability is recorded on the consolidated balance sheet for all leases except those with an original lease term of twelve months or less. Most of these leases include one or more renewal options, and certain leases also include lessee termination options. As these renewal options are not generally considered reasonably certain of exercise, they are not included in the lease term. The Company leases certain branch and corporate offices, land and ATM facilities through operating leases with terms typically ranging from 1 to 15 years, with the longest term having a lease expiration of March 31, 2034. The Company has no significant financing leases as of December 31, 2020. The following table summarizes the ROU asset and lease liability as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 (dollars in thousands) ROU asset $ 21,264 $ 22,709 Total lease liability 22,586 24,114 Weighted average remaining lease term 6.21 years 6.29 years Weighted average discount rate ¹ 1.82 % 1.83 % 1 The Company uses its incremental borrowing rate to calculate the present value of lease payments when the interest rate implicit in the lease is not disclosed. Total lease expense incurred by the Company was $1.7 million for both the three months ended December 31, 2020 and 2019, principally made up of contractual lease payments for operating leases. As of December 31, 2020 and September 30, 2020, the Company had no operating leases that had not yet commenced. The following table presents supplemental cash flow information related to leases for the three months ended December 31, 2020 and 2019: Three Months Ended December 31, 2020 2019 (dollars in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows paid for operating leases $ 1,482 $ 1,410 Right-of-use assets obtained in exchange for lease liabilities: Operating leases $ 987 $ 624 The following table presents a maturity analysis of the Company's operating lease liability as of December 31, 2020. Fiscal year Amount (dollars in thousands) Remaining in 2021 $ 4,383 2022 4,701 2023 4,149 2024 3,410 2025 2,469 2026 and thereafter 5,395 Total undiscounted lease payments 24,507 Less: Amounts representing interest (1,921) Lease liability $ 22,586

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase	3 Months Ended
	Dec. 31, 2020
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Abstract]
Securities Sold Under Agreements to Repurchase	Securities Sold Under Agreements to Repurchase Securities sold under agreements to repurchase generally mature overnight following the transaction date. Securities underlying the agreements had an amortized cost of approximately $93.6 million and $82.6 million and fair value of approximately $95.8 million and $84.7 million at December 31, 2020 and September 30, 2020, respectively. In most cases, in alignment with the repurchase agreements in place with customers, the Company over-collateralizes the agreements at 102% of total funds borrowed to protect the purchaser from changes in market value. Additionally, the Company utilizes held-in-custody procedures to ensure the securities sold under repurchase agreements are unencumbered. The following tables present the gross obligation by the class of collateral pledged and the remaining contractual maturity of the agreements at December 31, 2020 and September 30, 2020. December 31, 2020 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total (dollars in thousands) Repurchase agreements Mortgage-backed securities $ 80,355 $ — $ — $ — $ 80,355 Total repurchase agreements $ 80,355 $ — $ — $ — $ 80,355 September 30, 2020 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total (dollars in thousands) Repurchase agreements Mortgage-backed securities $ 65,506 $ — $ — $ — $ 65,506 Total repurchase agreements $ 65,506 $ — $ — $ — $ 65,506

FHLB Advances and Other Borrowi

FHLB Advances and Other Borrowings	3 Months Ended
	Dec. 31, 2020
Federal Home Loan Banks [Abstract]
FHLB Advances and Other Borrowings	FHLB Advances and Other Borrowings FHLB advances and other borrowings consist of the following at December 31, 2020 and September 30, 2020. December 31, September 30, (dollars in thousands) Short-term borrowings: Fed funds purchased, matured in October 2020 $ — $ 75,000 Long-term borrowings: Notes payable to FHLB, interest rates from 2.76% to 2.88% and maturity dates from September 2022 to September 2024 collateralized by real estate loans 120,000 120,000 Total $ 120,000 $ 195,000 As of December 31, 2020 and September 30, 2020, the Company had a borrowing capacity of $943.5 million and $947.7 million, respectively, with the FRB Discount Window. Principal balances of loans pledged to FRB Discount Window to collateralize the borrowing totaled $1.11 billion at December 31, 2020 and $1.17 billion at September 30, 2020. The Company has secured this line for contingency funding. As of December 31, 2020 and September 30, 2020, based on its collateral pledged, the additional borrowing capacity of the Company with the FHLB was $1.99 billion and $2.03 billion, respectively. Principal balances of loans pledged to the FHLB to collateralize notes payable totaled $3.93 billion and $4.07 billion at December 31, 2020 and September 30, 2020, respectively. The Company purchased letters of credit from the FHLB to pledge as collateral on public deposits. The amount outstanding was $0.0 million and $75.0 million at December 31, 2020 and September 30, 2020, respectively. The Company had additional letters of credit from the FHLB of $10.2 million and $14.6 million at December 31, 2020 and September 30, 2020, respectively, for other purposes. As of December 31, 2020, FHLB advances and other borrowings are due or callable (whichever is earlier) in subsequent fiscal years as follows. Fiscal year Amount (dollars in thousands) Remaining in 2021 $ — 2022 30,000 2023 30,000 2024 60,000 2025 — 2026 and thereafter — Total $ 120,000

Subordinated Debentures and Sub

Subordinated Debentures and Subordinated Notes Payable	3 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Subordinated Debentures and Subordinated Notes Payable	Subordinated Debentures and Subordinated Notes Payable Junior Subordinated Deferrable Interest Debentures The Company has seven trusts which were created or assumed as part of prior acquisitions that as of December 31, 2020 have 73,400 shares in the aggregate issued and outstanding, $1,000 par value, of Company Obligated Mandatorily Redeemable Preferred Securities ("Preferred Securities"). These seven trusts were established and exist for the sole purpose of issuing Preferred Securities and investing the proceeds in junior subordinated deferrable interest debentures ("Debentures") issued by the Company. The Debentures constitute the sole assets of the seven trusts. The Preferred Securities provide for cumulative cash distributions calculated at a rate based on three-month LIBOR plus a range from 1.48% to 3.35% adjusted quarterly. The Company may, at one or more times, defer interest payments on the Debentures for up to 20 consecutive quarters following suspension of dividends on all capital stock, but not beyond the respective maturity date. At the end of any deferral period, all accumulated and unpaid interest must be paid. The Debentures have redemption dates ranging from January 7, 2033 to October 1, 2037; however, the Company has the option to shorten the respective maturity date for all seven Preferred Securities as the initial call option date has passed. Holders of the Preferred Securities have no voting rights. The Preferred Securities are unsecured and rank junior in priority of the payment to all of the Company's indebtedness and senior to the Company's common and preferred stock. The trusts’ ability to pay amounts due on the Preferred Securities is solely dependent upon the Company making payment on the related Debentures. The Company’s obligation under the Debentures and relevant trust agreements constitute a full, irrevocable, and unconditional guarantee on a subordinated basis by it of the obligations of the trusts under the Preferred Securities. For regulatory purposes, the Debentures qualify as elements of capital. As of December 31, 2020 and September 30, 2020, Debentures, net of fair value adjustment, of $73.9 million and $73.8 million, respectively, were eligible for treatment as Tier 1 capital. Relating to the trusts, the Company held as assets $2.5 million in common shares at December 31, 2020 and September 30, 2020, which are included in other assets on the consolidated balance sheets. Subordinated Notes Payable In 2015, the Company issued $35.0 million of 4.875% fixed-to-floating rate subordinated notes that mature on August 15, 2025 through a private placement. The notes, whose eligibility as Tier 2 capital was reduced by 20% beginning in the quarter ended September 30, 2020, bear interest at a rate per annum equal to three-month LIBOR for the related interest period plus 3.15%, payable quarterly on each November 15, February 15, April 15 and August 15. The notes are subordinated in right of payment to all of the Company's senior indebtedness and effectively subordinated to all existing and future debt and all other liabilities of the Company's subsidiary bank. The Company may elect to redeem the notes (subject to regulatory approval), in whole or in part, on any early redemption date which is any interest payment date on or after August 15, 2020 at a redemption price equal to 100% of the principal amount plus any accrued and unpaid interest. Other than on an early redemption date, the notes cannot be accelerated except upon certain events of bankruptcy, insolvency or reorganization. Proceeds from the private placement of subordinated notes repaid outstanding subordinated debt. Subordinated debentures and subordinated notes payable are summarized as follows. December 31, 2020 September 30, 2020 Amount Outstanding Common Shares Held in Other Assets Amount Outstanding Common Shares Held in Other Assets (dollars in thousands) Junior subordinated debentures payable to non-consolidated trusts GW Statutory Trust IV, variable rate of 2.85%, plus 3 month LIBOR $ 23,093 $ 693 $ 23,093 $ 693 GW Statutory Trust VI, variable rate of 1.48%, plus 3 month LIBOR 30,928 928 30,928 928 SSB Trust II, variable rate of 1.85%, plus 3 month LIBOR 2,062 62 2,062 62 HF Capital Trust III, variable rate of 3.35%, plus 3 month LIBOR 5,155 155 5,155 155 HF Capital Trust IV, variable rate of 3.10%, plus 3 month LIBOR 7,217 217 7,217 217 HF Capital Trust V, variable rate of 1.83%, plus 3 month LIBOR 5,310 310 5,310 310 HF Capital Trust VI, variable rate of 1.65%, plus 3 month LIBOR 2,155 155 2,155 155 Total junior subordinated debentures payable 75,920 $ 2,520 75,920 $ 2,520 Less: fair value adjustment ¹ (2,054) (2,088) Total junior subordinated debentures payable, net of fair value adjustment 73,866 73,832 Subordinated notes payable Fixed to floating rate effective August 2020, 3.150% plus 3 month LIBOR 35,000 35,000 Total subordinated debentures and subordinated notes payable $ 108,866 $ 108,832 1 Adjustment reflects the fair value adjustments related to the junior subordinated deferrable interest debentures assumed as part of the HF Financial acquisition.

Profit Sharing Plan

Profit Sharing Plan	3 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Profit Sharing Plan	Profit Sharing PlanThe Company participates in a multiple employer 401(k) profit sharing plan ("401(k) Plan"). All employees are eligible to participate, beginning with the first day of the month coincident with or immediately following the completion of one year of service and having reached the age of 21. In addition to employee contributions, the Company may contribute discretionary amounts for eligible participants. Contribution rates for participating employees must be equal. The Company contributed $1.9 million and $1.7 million to the 401(k) Plan for the three months ended December 31, 2020 and December 31, 2019, respectively.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation On September 26, 2014, the Board of Directors adopted, and on October 10, 2014, NAB, at that time the Company's controlling shareholder, approved the Great Western Bancorp, Inc. 2014 Omnibus Incentive Compensation Plan ("2014 Plan"), the Great Western Bancorp, Inc. 2014 Non-Employee Director Plan ("2014 Director Plan"), and the Great Western Bancorp, Inc. Executive Incentive Compensation Plan ("Bonus Plan"), collectively ("the Plans"), which provide for the issuance of restricted share units and performance based share units to certain officers, employees and directors of the Company. On February 22, 2018, the Company's stockholders approved amendments to the 2014 Plan and the 2014 Director Plan to increase the number of shares available for future grants under the Plans. The Plans were primarily established to enhance the Company’s ability to attract, retain and motivate employees. The Company’s Board of Directors, the Compensation Committee of the Board of Directors ("Compensation Committee"), or executive management upon delegation of the Compensation Committee has exclusive authority to select the employees and others, including directors, to receive the awards and to establish the terms and conditions of each award made pursuant to the Company’s stock-based compensation plans. Stock units issued under the Company’s restricted and performance based stock plans may not be sold or otherwise transferred until the vesting period has been met and, if applicable, performance objectives have been obtained. During the vesting periods, participants do not have voting rights and dividends are accumulated until the time upon which the award vests. Upon specified events, as defined in the Plans, stock unit awards that have not vested and/or performance hurdles that have not been met will be forfeited. Based on the substantive terms of each award, restricted and performance-based awards are classified as equity awards and accounted for under the treasury stock method. The fair value of equity-classified awards is based on the market price of the stock on the measurement date and is amortized as compensation expense on a straight-line basis over the vesting or performance period. Stock compensation is recognized based on the number of awards expected to vest using actual forfeiture amounts. For performance-based stock awards, an estimate is made of the number of shares expected to vest as a result of actual performance against the performance targets to determine the amount of compensation expense to be recognized. The estimate is reevaluated quarterly and total compensation expense is adjusted for any change in the current period. Stock-based compensation expense is included in salaries and employee benefits expense in the consolidated statements of income. Stock compensation expense was $1.4 million for the three months ended December 31, 2020 and $1.6 million for the three months ended December 31, 2019. Related income tax benefits recognized were $0.3 million for the three months ended December 31, 2020 and $0.4 million for the three months ended December 31, 2019. The following is a summary of the Plans’ restricted share and performance-based stock award activity as of December 31, 2020 and September 30, 2020. The number of performance shares granted in the following table are reflected at the amount of achievement of the pre-established targets. December 31, 2020 September 30, 2020 Common Weighted-Average Grant Date Fair Value Common Weighted-Average Grant Date Fair Value Restricted Shares Restricted shares, beginning of fiscal year 249,180 $ 32.89 190,805 $ 37.20 Granted 152,028 17.30 147,282 30.68 Vested (79,093) 36.28 (84,316) 38.60 Forfeited (2,017) 28.89 (4,591) 36.18 Canceled — — — — Restricted shares, end of period 320,098 $ 24.67 249,180 $ 32.89 Vested, but not issuable at end of period 87,324 $ 29.32 62,992 $ 33.98 Performance Shares Performance shares, beginning of fiscal year 175,740 $ 33.56 173,332 $ 38.50 Granted 115,885 17.26 62,278 40.15 Vested (25,452) 41.07 (54,861) 39.43 Forfeited (11,904) 39.04 (5,009) 37.90 Canceled — — — — Performance shares, end of period 254,269 $ 25.12 175,740 $ 33.56 Vested, but not issuable at end of period 5,612 $ 18.00 5,612 $ 18.00

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures, monitors and discloses certain of its assets and liabilities on a fair value basis. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The fair value guidance also establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The guidance describes the following three levels of inputs that may be used to measure fair value: Level 1 Quoted prices in active markets for identical assets or liabilities; Level 2 Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Level 1 inputs are considered to be the most transparent and reliable and Level 3 inputs are considered to be the least transparent and reliable. The Company assumes the use of the principal market to conduct a transaction of each particular asset or liability being measured and then considers the assumptions that market participants would use when pricing the asset or liability. Whenever possible, the Company first looks for quoted prices for identical assets or liabilities in active markets (Level 1 inputs) to value each asset or liability. However, when inputs from identical assets or liabilities on active markets are not available, the Company utilizes market observable data for similar assets and liabilities. The Company maximizes the use of observable inputs and limits the use of unobservable inputs to occasions when observable inputs are not available. The need to use unobservable inputs generally results from the lack of market liquidity of the actual financial instrument or of the underlying collateral. Although in some instances, third party price indications may be available, limited trading activity can challenge the observability of these quotations. Assets and Liabilities Measured at Fair Value on a Recurring Basis Following is a description of the valuation methodologies and inputs used for assets and liabilities measured at fair value on a recurring basis and recognized in the accompanying consolidated balance sheets, as well as the general classification of such assets and liabilities pursuant to the valuation hierarchy. Securities Available for Sale Where quoted market prices are available in an active market, securities are classified within Level 1 of the valuation hierarchy. Level 1 securities include U.S. Treasury securities. If quoted market prices are not available, then fair values are estimated by using pricing models, quoted prices of securities with similar characteristics, or discounted cash flows and classified as Level 2 securities. Level 2 securities include mortgage-backed, states and political subdivisions, and other securities. Where Level 1 or Level 2 inputs are not available, securities are classified within Level 3 of the hierarchy. Level 3 securities were immaterial at December 31, 2020 and September 30, 2020. Interest Rate Swaps and Loans Interest rate swaps are valued by the Company's Swap Dealers using cash flow valuation techniques with observable market data inputs. The fair value of loans accounted for under the fair value option represents the net carrying value of the loan, plus the equal and opposite amount of the value of the swap needed to offset the interest rate risk and an adjustment for credit risk based on the Company's assessment of existing market conditions for the specific portfolio of loans. This is used due to the strict prepayment penalties put in the loan terms to cover the cost of exiting the interest rate swap of the loans in the case of early prepayment or termination. The adjustment for credit risk on loans accounted for under the fair value option is not significant to the overall fair value of the loans. The fair values estimated by the Company's Swap Dealers use interest rates that are observable or that can be corroborated by observable market data and, therefore, are classified within Level 2 of the valuation hierarchy. The Company has entered into Collateral Agreements with its Swap Dealers and Futures Clearing Merchant which entitle it to receive collateral to cover market values on derivatives which are in asset position, thus a credit risk adjustment on interest rate swaps is not warranted. The Company regularly enters into interest rate lock commitments on mortgage loans to be held for sale with corresponding forward sales contracts related to these interest rate lock commitments, the fair values of which are calculated by applying observable market values from Fannie Mae TBA pricing to each interest rate lock commitment and forward sales contract, therefore, are classified within Level 2 of the valuation hierarchy. The Company also has back-to-back swaps with loan customers, with corresponding swaps with an outside third party in exact offsetting terms. Loan Servicing Rights Fair value is determined at a tranche level, based on market prices for comparable mortgage servicing contracts (Level 3), when available, or alternatively based on a valuation model that calculates the present value of estimated future net servicing income. The valuation model utilizes interest rate, prepayment speed, and default rate assumptions that market participants would use in estimating future net servicing income and that can be validated against market data (Level 3). The following table presents the fair value measurements of assets and liabilities recognized in the accompanying consolidated balance sheets measured at fair value on a recurring basis and the level within the fair value hierarchy in which the fair value measurements fall at December 31, 2020 and September 30, 2020. Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of December 31, 2020 U.S. Treasury securities $ 25,014 $ 25,014 $ — $ — U.S. Agency securities 24,703 24,703 — — Mortgage-backed securities 1,956,431 — 1,956,431 — States and political subdivision securities 52,417 — 48,751 3,666 Other 1,050 — 1,050 — Total securities available for sale $ 2,059,615 $ 49,717 $ 2,006,232 $ 3,666 Derivatives-assets $ 88,261 $ — $ 88,261 $ — Derivatives-liabilities 324 — 324 — Fair value loans 611,588 — 611,588 — Loan servicing rights 1,063 — — 1,063 Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of September 30, 2020 U.S. Treasury securities $ 50,152 $ 50,152 $ — $ — U.S. Agency securities 25,060 25,060 — — Mortgage-backed securities 1,642,780 — 1,642,780 — States and political subdivision securities 55,580 — 51,783 3,797 Other 1,054 — 1,054 — Total securities available for sale $ 1,774,626 $ 75,212 $ 1,695,617 $ 3,797 Derivatives-assets $ 98,380 $ — $ 98,380 $ — Derivatives-liabilities 98 — 98 — Fair value loans 655,185 — 655,185 — Loan servicing rights 1,303 — — 1,303 The following table presents the changes in Level 3 assets and liabilities measured at fair value on a recurring basis for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 (dollars in thousands) Other securities available for sale Balance, beginning of period $ 3,797 $ 4,120 Additions — — Principal paydown (131) (134) Balance, end of period $ 3,666 $ 3,986 Loan servicing rights Balance, beginning of period $ 1,303 $ 2,255 Realized and unrealized loss ¹ (240) (201) Balance, end of period $ 1,063 $ 2,054 1 Realized and unrealized loss related to loan servicing rights are reported as a component of mortgage banking income, net on the consolidated statements of income. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Following is a description of the valuation methodologies used for assets and liabilities measured at fair value on a nonrecurring basis and recognized in the accompanying consolidated balance sheets, as well as the general classification of such assets and liabilities pursuant to the valuation hierarchy. Other Repossessed Property Other repossessed property consists of loan collateral that has been repossessed through foreclosure. This collateral is comprised of commercial and residential real estate and other repossessed assets. Other repossessed property is recorded initially at fair value of the collateral less estimated selling costs. Subsequent to foreclosure, valuations are updated periodically, and the assets may be marked down further to fair value less selling costs, reflecting a valuation allowance. Fair value measurements may be based upon appraisals, third-party price opinions, or internally developed pricing methods. These measurements are classified as Level 3. Impaired Loans (Collateral Dependent) Loans for which it is probable that the Company will not collect all principal and interest due according to contractual terms are measured for impairment. Allowable methods for estimating fair value include using the fair value of the collateral for collateral dependent loans or, where a loan is determined not to be collateral dependent, using the discounted cash flow method. If the impaired loan is identified as collateral dependent, then the fair value method of measuring the amount of the impairment is utilized. This method requires obtaining a current independent appraisal of the collateral and applying a discount factor, if necessary, to the appraised value and including costs to sell. Because many of these inputs are not observable, the measurements are classified as Level 3. Mortgage Loans Held for Sale Fair value of mortgage loans held for sale is based on either quoted prices for the same or similar loans, or values obtained from third parties, or are estimated for portfolios of loans with similar financial characteristics and are therefore considered a Level 2 valuation. Property Held for Sale This real estate property is carried in premises and equipment as property held for sale at fair value based upon the transactional price if available, or the appraised value of the property. The following table presents the fair value measurement of assets and liabilities measured at fair value on a nonrecurring basis and the level within the fair value hierarchy in which the fair value measurements fall at December 31, 2020 and September 30, 2020. Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of December 31, 2020 Other repossessed property $ 8,594 $ — $ — $ 8,594 Impaired loans 275,334 — — 275,334 Mortgage loans held for sale, at lower of cost or fair value 11,638 — 11,638 — Property held for sale 600 — — 600 As of September 30, 2020 Other repossessed property $ 17,991 $ — $ — $ 17,991 Impaired loans 669,968 — — 669,968 Mortgage loans held for sale, at lower of cost or fair value 12,371 — 12,371 — Property held for sale 600 — — 600 The valuation techniques and significant unobservable inputs used to measure Level 3 fair value measurements at December 31, 2020 were as follows. Fair Value of Assets / (Liabilities) at December 31, 2020 Valuation Unobservable Range Weighted (dollars in thousands) Other repossessed property $ 8,594 Appraisal value Collateral specific adjustment N/A N/A Impaired loans 275,334 Appraisal value Collateral specific adjustment N/A N/A Property held for sale 600 Appraisal value Collateral specific adjustment N/A N/A Disclosures about Fair Value of Financial Instruments Significant assets and liabilities that are not considered financial instruments are accounted for at amortized cost and include premises and equipment, deferred income taxes, goodwill, and core deposit and other intangibles. Additionally, in accordance with the disclosure guideline, receivables and payables due in one year or less, insurance contracts, equity investments not accounted for at fair value, and deposits with no defined or contractual maturities are excluded. Off-balance sheet instruments (commitments to extend credit and standby letters of credit) are generally short-term and at variable rates. Therefore, both the carrying amount and the estimated fair value associated with these instruments are immaterial. Fair values for on-balance sheet instruments as of December 31, 2020 and September 30, 2020 are as follows. December 31, 2020 September 30, 2020 Level in Fair Value Hierarchy Carrying Amount Fair Carrying Amount Fair (dollars in thousands) Assets Cash and cash equivalents Level 1 $ 1,061,796 $ 1,061,796 $ 432,887 $ 432,887 Loans, net, excluding fair valued loans, loans held for sale and impaired loans ¹ Level 3 8,619,316 8,623,172 8,738,617 8,768,314 Liabilities Time deposits Level 2 1,078,580 1,082,378 1,282,978 1,287,814 FHLB advances and other borrowings Level 2 120,000 129,077 195,000 204,715 Securities sold under repurchase agreements Level 2 80,355 80,355 65,506 65,506 Subordinated debentures and subordinated notes payable Level 2 108,866 93,213 108,832 96,424 1 Includes $29.2 million and $29.0 million of net deferred loan fees at December 31, 2020 and September 30, 2020, respectively, of which carrying value approximates fair value.

Earnings per Share

Earnings per Share	3 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share Basic earnings per common share is calculated by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per common share is calculated by dividing net income available to common shareholders by the weighted average number of common shares outstanding determined for the basic earnings per share calculation plus the dilutive effect of stock compensation using the treasury stock method. The following information was used in the computation of basic and diluted earnings per share (EPS) for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 (dollars in thousands, except per share data) Net income $ 41,319 $ 43,274 Weighted average common shares outstanding 55,119,909 56,377,631 Dilutive effect of stock based compensation 127,434 80,336 Weighted average common shares outstanding for diluted earnings per share calculation 55,247,343 56,457,967 Basic earnings per share $ 0.75 $ 0.77 Diluted earnings per share $ 0.75 $ 0.77 The Company had 115,160 and no shares of unvested performance stock as of December 31, 2020 and 2019, respectively, which were not included in the computation of diluted earnings per common share because performance conditions for vesting had not been met. The Company had 169,539 and 66,155 shares of anti-dilutive stock awards outstanding as of December 31, 2020 and 2019, respectively.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition The Company recognizes revenue from contracts with customers in accordance with ASC Topic 606, Revenue from Contracts with Customers . The core principle requires an entity to recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration it expects to be entitled to receive in exchange for those goods or services recognized as performance obligations are satisfied. The majority of the Company's revenue-generating transactions are not subject to ASC Topic 606, including revenue generated from financial instruments, such as loans, letters of credit, derivatives and investment securities, as well as revenue related to mortgage servicing activities, as these activities are subject to other GAAP and discussed elsewhere within Item 8. Financial Statements and Supplementary Data, "Note 1. Nature of Operations and Summary of Significant Accounting Policies" in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. Descriptions of the Company's revenue-generating activities that are within the scope of ASC Topic 606, which are presented in the consolidated income statements as components of noninterest income, are as follows: Service charges and fees on deposit accounts. Service charges on deposit accounts are earned for account maintenance and overdraft, wire and treasury management services. Revenue is recognized at the time the services are performed and is included in service charges and other fees within noninterest income on the consolidated statements of income. Interchange and merchant services income. Interchange and merchant services income are earned from credit and debit card payment processing through card association networks, merchant services and other card related services. Fees for these services are primarily based on interchange rates set by the networks and transaction volumes and are recognized as transactions are processed and settled with networks on behalf of card holders. These fees are presented net of direct expenses, including reward costs, associated with credit and debit card interchange income in service charges and other fees which are included in noninterest income on the consolidated statements of income. Wealth management and trust fee income. Wealth management and trust fees are earned for asset management, custody and recordkeeping, investment advisory and administrative services. Revenue is recognized as the services are performed. Brokerage charges are recorded as a net reduction in wealth management fees which are included in noninterest income on the consolidated statements of income. Other noninterest income. Other noninterest income primarily includes such items as letter of credit fees, gains on sale of loans held for sale and servicing fees, none of which are subject to the requirements of ASC Topic 606. The following table presents total noninterest income segregated between contracts with customers within the scope of ASC Topic 606 and those within the scope of other GAAP Topics. The following additionally presents revenues from customers that are included within noninterest income. Three Months Ended December 31, 2020 2019 (dollars in thousands) Noninterest income Service charges and other fees $ 9,624 $ 11,409 Wealth management fees 3,029 2,964 Other 848 668 Noninterest income from contracts with customers within the scope of ASC Topic 606 13,501 15,041 Noninterest income within the scope of other GAAP Topics ¹ 647 692 Total noninterest income $ 14,148 $ 15,733 1 The Company presents out of scope noninterest income for the purpose of reconciling noninterest income amounts within the scope of ASC Topic 606 to noninterest income amounts presented on the Company's consolidated statements of income.

Nature of Operations and Summ_2

Nature of Operations and Summary of Significant Policies (Policies)	3 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated interim financial statements have been prepared in accordance with GAAP and reflect all adjustments that are, in the opinion of management, necessary for the fair presentation of the financial position and results of operations for the periods presented. All such adjustments are of a normal recurring nature. Certain previously reported amounts have been reclassified to conform to the current presentation. The unaudited interim consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements for the year ended September 30, 2020, which includes a description of significant accounting policies. The results of operations for interim periods are not necessarily indicative of the results that may be expected for the year or any other period. The accompanying unaudited consolidated financial statements include the accounts and results of operations of the Company and its subsidiaries after elimination of all significant intercompany accounts and transactions. The preparation of unaudited consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the amounts reported on the consolidated financial statements and accompanying notes. Actual results could differ from these estimates.
Securities	Securities Purchases and sales of securities are recognized on a trade date basis. The cost of securities sold is based on the specific identification method. The Company classifies securities upon purchase in one of three categories: trading, held to maturity, or available for sale. Debt securities held for resale are classified as trading. Debt securities for which the Company has the ability and positive intent to hold until maturity are classified as held to maturity. All other securities are classified as available for sale as they may be sold prior to maturity in response to changes in the Company’s interest rate risk profile, funding needs, demand for collateralized deposits by public entities or other reasons. Interest and dividends, including amortization of premiums and accretion of discounts, are recognized as interest income when earned. Trading securities are stated at fair value. Realized and unrealized gains and losses from sales and fair value adjustments of trading securities are included in other noninterest income on the consolidated statements of income. Available for sale securities are stated at fair value. For available for sale debt securities in an unrealized loss position, management first evaluates whether (1) the Company has the intent to sell a security; or (2) it is more-likely-than-not that the Company will be required to sell the security before recovery of its amortized cost basis. If either criteria is met, the entire amount of unrealized loss is recognized in the consolidated income statement with a corresponding adjustment to the security's amortized cost basis. If neither criteria is met, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. Furthermore, securities issued by the U.S. Government or a U.S. Government sponsored enterprise which carry the explicit or implicit guarantee of the U.S. Government are considered "risk-free" and therefore no credit losses are assumed on those securities. If the assessment indicates a credit loss exists, the amortized cost basis is compared to the present value of cash flows expected to be collected from the security; if it is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded. Changes in the allowance for credit losses are recorded as a provision for (reversal of) credit losses in the consolidated income statement. If the assessment indicates a credit loss does not exist, the change in fair value is recorded as unrealized gains and losses, net of related taxes, and is included in stockholders’ equity as a component of accumulated other comprehensive income (loss). Equity securities are carried at fair value, with changes in fair value reported in the consolidated statements of income. Equity securities without readily determinable fair values are carried at cost, minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment.
Loans	Loans Originated Loans Loans that management has the intent and ability to hold for the foreseeable future, or until maturity or pay-off, are reported at amortized cost (i.e., outstanding principal balance, adjusted for charge-offs and any unamortized deferred fees or costs). Other fees not associated with originating a loan are recognized as fee income when earned. Interest income on loans is accrued daily on the outstanding balances. A loan is placed on nonaccrual status when management believes, after considering collection efforts and other factors, the borrower's condition is such that collection of interest is doubtful, which is generally 90 days past due. When loans are placed on nonaccrual status, accrual of interest is discontinued and interest receivable is reversed against interest income in the current period. Interest payments received thereafter are applied as a reduction to the remaining principal balance as long as concern exists as to the ultimate collection of the principal. Loans are removed from nonaccrual status when they become current as to both principal and interest and concern no longer exists as to the collectability of principal and interest. For loans held for sale, loan fees charged or received on origination, net of certain direct loan origination costs, are recognized in income when the related loan is sold. For loans held for investment, loan fees, net of certain direct loan origination costs, are deferred and the net amount is amortized as an adjustment of the related loan’s yield. The Company is generally amortizing these amounts over the contractual lives of the loans. Commitment fees are recognized as income when received. The Company makes commercial, agricultural, residential real estate, consumer and other loans to customers primarily in Arizona, Colorado, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota and South Dakota. The amount of collateral obtained, if deemed necessary, is based on management’s credit evaluation of the borrower. Collateral held varies but includes accounts receivable, marketable securities, inventory, equipment and real estate. Personal guarantees of the borrower or related parties and government guarantees are also obtained for some loans, which reduces the Company’s risk of loss. Loans originated and intended for sale in the secondary market are carried at the lower of cost or fair value. Loans held for sale include fixed rate single-family residential mortgage loans under contract to be sold in the secondary market. In most cases, loans are carried at cost and sold within 45 days. These loans are sold with the mortgage servicing rights released. Under limited circumstances, buyers may have recourse to return a purchased loan to the Company. Recourse conditions may include early payment default, breach of representation or warranties, or documentation deficiencies. Fair value of loans held for sale is determined based on prevailing market prices for loans with similar characteristics, sale contract prices, or, for certain portfolios, discounted cash flow analysis. Declines in fair value below cost (and subsequent recoveries) are recognized in net gain on sale of loans. Deferred fees and costs related to these loans are not amortized but are recognized as part of the cost basis of the loan at the time it is sold. Gains or losses on sales are recognized upon delivery and included in net gain on sale of loans. Loans at Fair Value Under the Fair Value Option ("FVO loans") The Company has elected to measure certain long-term loans and written loan commitments at fair value to assist in managing interest rate risk for longer-term loans. Fair value loans are fixed-rate loans having original maturities of 5 years or greater (typically between 5 and 15 years) to our business and agri-business banking customers to assist them in facilitating their risk management strategies. The fair value option was elected upon the origination or acquisition of these loans and written loan commitments. Interest income is recognized in the same manner on loans reported at fair value as on non-fair value loans, except in regard to origination fees and costs which are recognized immediately upon closing. The Company has also entered into interest rate derivative contracts to convert these long term fixed rate loans to variable rates. These contracts do not quality for hedge accounting and instead these interest rate derivative instruments are recognized as other assets or other liabilities on the consolidated balance sheets and measured at fair value, with changes in fair value reported in change in fair value of FVO loans and related derivatives on the consolidated statements of income. Since each fixed rate loan is paired with an offsetting derivative contract, the impact to net income is minimized. When determined necessary, a credit mark is applied against the valuation of the asset that reflects the borrower's credit worthiness. Changes in the credit mark are included in change in fair value of FVO loans and related derivatives on the consolidated statements of income. Credit Risk Management The Company uses several credit quality indicators to manage credit risk in an ongoing manner. The Company’s strategy for credit risk management includes well-defined, centralized credit policies, uniform underwriting criteria and ongoing risk monitoring and review processes for all credit exposures. The strategy also emphasizes diversification on a geographic, industry, loan class type, and customer level; regular credit examinations; and management reviews of loans exhibiting deterioration of credit quality. The credit risk management strategy also includes a credit risk assessment process that performs assessments of compliance with commercial and consumer credit policies, risk ratings, and other critical credit information. Loan decisions are documented with respect to the borrower’s business, purpose of the loan, evaluation of the repayment sources, and the associated risks, evaluation of collateral, covenants and monitoring requirements, and risk rating rationale. The Company assigns all non-consumer loans a credit quality risk rating. The Company implemented a more granular risk rating methodology as of October 1, 2020. See the table below for a summary of credit quality risk ratings at December 31, 2020. For information on the credit quality risk ratings in effect before October 1, 2020, see "1. Nature of Operations and Summary of Significant Accounting Policies" in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. Credit Quality Credit Quality Indicators Pass Commercial loans within this category are not adversely rated, current as to principal and interest, and are otherwise in compliance with the contractual terms of the loan agreement. Management believes there is a low likelihood of loss related to loans in this category. Special Mention Commercial loans within this category have potential weaknesses that deserve management's close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or in the Company's credit position at some future date. Special mention assets are not adversely classified and do not expose the Company to sufficient risk to warrant an adverse classification. Substandard Commercial loans within this category are inadequately protected by the current sound worth and paying capacity of the borrower or of the collateral pledged, if any. Assets so classified must have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans in this category are assigned a workout loan officer to closely monitor the relationship. Doubtful Commercial loans within this category are considered uncollectible and of such little value that their continuance as bankable assets is not warranted. This classification does not mean that the asset has absolutely no recovery or salvage value, but rather that it is not practical or desirable to defer writing off this basically worthless asset even though partial recovery may be effected in the future. Revolving lines of credit rated Substandard or Doubtful require a higher level of approval and are reviewed quarterly. Advances are allowed to support the continued operating needs of the borrower for their operation and may include, but not limited to, working capital needs to support inventory, accounts receivable, payroll, tax payments, utilities and other needs to operate the business. All non-consumer loan risk ratings are monitored by management and updated as deemed appropriate. The Company generally does not risk rate residential real estate or consumer loans unless a default event such as bankruptcy or extended nonperformance takes place. Alternatively, delinquencies are monitored and standard credit scoring systems are used to assess credit risks of residential real estate and consumer loans. Troubled Debt Restructurings Loans modified under troubled debt restructurings involve granting a concession to a borrower who is experiencing financial difficulty. These concessions could include a reduction in the interest rate on the loan, payment extensions, forgiveness of principal, forbearance, or other actions intended to maximize collection, which generally would not otherwise be considered. The Company's TDRs include performing and nonperforming TDRs, which consist of loans that continue to accrue interest at the loan's original interest rate when the Company expects to collect the remaining principal and interest on the loan, and nonaccrual TDRs, which include loans that are in a nonaccrual status and are no longer accruing interest, as the Company does not expect to collect the full amount of principal and interest owed from the borrower on these loans. At the time of modification (except for loans on nonaccrual status), a TDR is classified as nonperforming TDR until a six-month payment history of principal and interest payments, in accordance with the terms of the loan modification, is sustained, at which time the loan is moved to a performing status (performing TDR). If the Company does not expect to collect all principal and interest on the loan, the modified loan is classified as a nonaccrual TDR. All TDRs are accounted for as impaired loans and are included in the analysis of the allowance for credit losses. A TDR that has been renewed for a borrower who is no longer experiencing financial difficulty and which yields a market rate of interest at the time of a renewal is no longer considered a TDR. In March 2020, a statement was issued by our banking regulators titled "Interagency Statement on Loan Modifications and Reporting for Financial Institutions Working with Customers Affected by the Coronavirus" that encourages financial institutions to work prudently with borrowers who are or may be unable to meet their contractual payment obligations due to the effects of COVID-19. Additionally, Section 4013 of the CARES Act further provides that a qualified loan modification is exempt by law from classification as a TDR as defined by GAAP, from the period beginning March 1, 2020 until December 31, 2020. In December 2020, the Economic Aid to Hard Hit Small Businesses, Non-Profits, and Ventures Act was enacted, which extended the TDR provisions of the CARES Act to January 1, 2022. Accordingly, we are offering short-term modifications made in response to COVID-19 to borrowers who are current and otherwise not past due. These include short-term, 180 days or less, modifications in the form of payment deferrals, fee waivers, extensions of repayment terms, or other delays in payment that are insignificant.
Allowance for Credit Losses ("ACL")	Allowance for Credit Losses ("ACL") The Company adopted ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, and subsequent related ASUs, on October 1, 2020, which uses the current expected credit loss model ("CECL") to determine the allowance for credit losses based on an ongoing evaluation, driven primarily by monitoring changes in loan risk grades, delinquencies, and other credit risk indicators, which are inherently subjective. The measurement of expected credit losses under the CECL methodology is applicable to financial assets measured at amortized cost, including loans receivables and held-to-maturity debt securities. It also applies to off-balance sheet credit exposures not accounted for as insurance (loan commitments, standby letters of credit, financial guarantees, and other similar instruments) and the net investments in leases recognized by a lessor in accordance with Topic 842 on leases. The CECL methodology requires recognition of lifetime expected credit losses that takes into consideration all relevant information, including historical losses, current conditions and reasonable and supportable forecasts of future operating conditions. Loans that do not share similar risk characteristics and are collateral dependent, primarily large loans on nonaccrual status and those which have undergone a TDR, are evaluated on an individual basis ("individual reserve"). The reserve related to these loans is using the collateral available to repay the loan, most typically the liquidation value of the collateral (less selling costs, if applicable). The Company has chosen to continue to include small, less complex loans within the collective reserve for loans on nonaccrual or with TDR status. Loans that are not reserved for on an individual basis are measured on a collective, or pooled basis ("collective reserve"). Loans are aggregated into pools (or segments) based on similar risk characteristics including borrower type, collateral, type and expected credit loss patterns. The historical loss experience of the pool is generally the starting point for estimating expected credit losses under the collective reserve methodology. The historical loss experience rate of the loan segment is applied to each loan within the segment over the contractual life of each loan, adjusted for estimated prepayments. Management then determines an appropriate macroeconomic forecast based on the expectation of future conditions, including but not limited to the unemployment rate, which is the most significant factor, gross domestic product and corporate bond spreads, and applies the forecast to models which estimate the change in loss expectations relative to the historical loss rates. These models have been implemented in accordance with the Company's Model Risk Management Policy. Additionally, using its new risk rating system, the Company evaluates if the current credit quality of the portfolio materially differs from the one observed over the historical loss period and applies adjustments to the allowance accordingly. Qualitative adjustments may also be made to expected losses based on current and future conditions that may not be fully captured in the modeling components above, such as but not limited to industry, geographic and borrower concentrations, loans servicing practices and changes in underwriting criteria. ASU 2016-13 requires institutions to establish a supportable forecast and reversion period for forecasted operating conditions. Management determined a two-year forecast period would capture the majority of the impact associated with current economic conditions and is short enough to be supportable. Additionally, loss rate forecasts follow a straight-line reversion back to the historical loss rate over one year following the initial forecast period. The following table describes the Company’s eight loan portfolio pools, which is the level at which it develops and documents a systematic methodology to determine the allowance for credit losses. Loan Segment Composition Collateral Primary Source of Repayment Key Risk Characteristics Construction and development 1 Commercial and residential construction loans Secured by commercial and residential real estate Cash flows Industry and geography of borrower's business, purpose of the loan, repayment sources, borrower's capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Owner-occupied CRE Small and middle market businesses Secured by commercial real estate Non-owner-occupied CRE Multifamily residential real estate Agriculture Agri-business operating and real estate loans Secured by operating assets, agricultural real estate, and guarantees of owners Cash flows Geography of the borrower's operations, commodity type and prices and weather patterns, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Commercial non-real estate Small and middle market businesses and loans made to public sector Secured by business assets and guarantees of owners Cash flows Industry and geography of the borrower's business, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Residential real estate Residential mortgages and home equity loans and lines Secured by residential real estate Borrower's income Borrower's capacity and willingness to repay, unemployment rates and other economic factors, and customer repayment history Consumer and other Consumer loans and all other loan relationships that do not fit within categories above, including consumer and commercial credit cards and consumer deposit account overdrafts Secured by automobiles, unsecured 1 Residential real estate construction loans are included in the construction and development segment until construction is completed, after which the loan is moved to the residential real estate loan segment. Changes to the allowance for credit losses are made by charges to the provision for credit losses, which is reflected on the consolidated statements of income. Past due status is monitored as an indicator of credit deterioration. Loans deemed to be uncollectible are charged off against the allowance for credit losses. Recoveries of amounts previously charged-off are credited to the allowance for credit losses. Unfunded Commitments and Unfunded Commitments Reserve Unfunded residential mortgage loan commitments entered into in connection with mortgage loans to be held for sale are considered derivatives and are recorded at fair value and included in accrued expenses and other liabilities on the consolidated balance sheets with changes in fair value recorded in other interest income in the consolidated statements of income. All other unfunded loan commitments are generally related to providing credit facilities to customers and are not considered derivatives. The unfunded commitments reserve ("unfunded reserve") presents the expected credit losses on off-balance sheet commitments such as unfunded commitments to extend credit and standby letters of credit. An unfunded reserve is not recognized for commitments unconditionally cancellable by the Company, which includes credit cards, warehouse lines of credit and other revolving lines which are deemed to be unconditionally cancellable and is recorded in accrued expenses and other liabilities on the consolidated balance sheet. Changes to the unfunded reserve are recognized in provision for credit losses in the consolidated statements of income. The unfunded reserve is determined by estimating future draws and applying the expected loss rates on those draws. Future draws are based on historical averages of utilization rates (i.e., the likelihood of draws taken). Loss rates are estimated by utilizing the same loss rates calculated for the collective reserve of the allowance for credit losses. The Company's change in unfunded commitments reserve from the incurred loss methodology to the current expected credit loss methodology was immaterial as of the date of adoption and therefore no provision was recognized. Accrued Interest Receivable Upon adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, the Company has elected the following: • Accrued interest receivable balances are presented separately within the consolidated balance sheets, • Accrued interest receivable balances are excluded from amortized cost of financing receivables and related disclosure requirements, and • Uncollectible accrued interest receivable is written off by reversing interest income, generally upon becoming 90 days past due.
Subsequent Events	Subsequent Events The Company has evaluated all events or transactions that occurred through the date the Company issued these financial statements. Other than those described below, there were no material events or transactions that would require recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements.
New Accounting Standards	Accounting Standards Adopted in Fiscal Year 2021 In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, which address recording of estimated lifetime credit losses on loans, including funded and unfunded commitments, and other financial instruments held by financial institutions and other organizations. ASU 2016-13, as amended, requires institutions to measure all expected credit losses related to financial assets measured at amortized cost with an expected loss model based on historical experience, current conditions and reasonable and supportable forecasts relevant to affect the collectability of the financial assets, which is referred to as the CECL model. ASU 2016-13, as amended, requires enhanced disclosures, including qualitative and quantitative requirements, to help understand significant estimates and judgments used in estimating credit losses, as well as provide additional information about the amounts recorded in the financial statements. The measurement of expected losses under CECL is applicable to financial assets measured at amortized cost, including loan receivables and debt securities held to maturity. It also applies to off-balance sheet credit exposures not accounted for as insurance (loan commitments, standby letters of credit and other similar instruments). In addition, CECL requires debt securities available for sale with an unrealized loss to be recognized as allowance for credit loss rather than as a write-down of the securities amortized cost basis when management intends to sell or believes that it is not more-likely-than-not that they will be required to sell the securities prior to recovery of the securities amortized cost to be recognized as allowance for credit loss rather than as a write-down of the securities amortized cost basis . The CECL standard does not apply to the loan portfolio accounted for using the fair value option. The Company identified eight loan portfolio segments for which a model has been established to estimate credit losses. The historical data sets of these segments were identified, populated and validated. Each segment contains loans which have similar risk characteristics. Not unlike the incurred loss model, each segment is split into loans that are individually assessed and those that are collectively assessed. The Company adopted the standard on October 1, 2020, and applied the standard's provisions under the modified retrospective approach. Upon adoption of the standard, the Company recorded a $177.3 million increase to the ACL, of which $1.5 million related to the transfer of discounts on previously acquired loans and $175.8 million related to changes from the incurred loss model to the CECL model, which resulted in a cumulative effect adjustment decrease of $132.9 million (after-tax) to retained earnings. The tax effect resulted in a $42.9 million increase in deferred tax assets. In addition, the Company has elected the 5 year CECL transition for regulatory capital ratios, resulting in an add-back of $129.5 million to common equity tier 1 capital as of December 31, 2020. The Company did not record an allowance for available for sale or held to maturity securities upon adoption as the investment portfolio consisted primarily of debt securities explicitly or implicitly backed by the U.S. Government for which expected credit loss is zero. We adopted the CECL standard using the prospective transition approach for financial assets purchased with credit deterioration ("PCD") that were previously classified as purchased credit impaired ("PCI") and accounted for under ASC 310-30. In accordance with the standard, we did not reassess whether PCI assets met the definition of PCD assets as of the date of adoption. On October 1, 2020, the Company determined $1.5 million of existing discounts on PCD loans was related to credit factors and was reclassified to the ACL. The remaining noncredit discount of $6.7 million was determined to be related to noncredit factors and will be accreted into interest income on a level-yield method over the remaining life of the loans. For additional information, see "Note 1. Nature of Operations and Summary of Significant Policies", "Note 3. Securities Available for Sale", and "Note 4. Loans and Allowance for Credit Losses." Accounting Standards Not Yet Adopted in Fiscal Year 2021 In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes in the Disclosure Requirements for Fair Value Measurement , which eliminates, adds 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. ASU 2018-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted. Entities are also allowed to elect to early adopt the eliminated or modified disclosure requirements and delay adoption of the new disclosure requirements until after their effective date. As ASU 2018-13 only revises disclosure requirements, the Company does not believe this ASU will have a material impact on the consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , which aims to simplify the accounting for income taxes by removing certain exceptions to the general principles and also simplification of areas such as franchise taxes, step-up in tax basis goodwill, separate entity financial statements and interim recognition of enactment of tax laws or rate changes. The ASU will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company is currently evaluating the potential impact of ASU 2019-12 on the consolidated financial statements. In January 2020, the FASB issued ASU 2020-01, Investments - Equity Securities (Topic 321), Investments - Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815): Clarifying the Interactions between Topic 321, Topic 323 and Topic 815 , which clarifies that an entity should consider observable transactions that require it to either apply or discontinue the equity method of accounting for the purposes of applying the fair value measurement alternative. The ASU will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020, with early adoption permitted. The Company does not expect adoption to have a material impact on the consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting , which provides optional expedients and exceptions for a limited time period to ease the potential burden in accounting for reference rate reform on financial reporting. The amendments in ASU 2020-04 are elective for entities with contracts, including derivative contracts, that reference LIBOR or some other reference rate that are expected to be discontinued. For the Company's cash flow hedges, ASU 2020-04 allows: (i) an entity to change the reference rate without having to designate the hedging relationship; (ii) for cash flow hedges in which the designated hedged risk is LIBOR, allows an entity to assert that it remains probable that the hedged forecasted transaction will occur; and (iii) allows an entity to change the designated method used to assess hedge effectiveness and simplifies or temporarily suspends the assessment of hedge effectiveness for hedging relationships. ASU 2020-04 must be applied prospectively and was effective immediately upon issuance and remains effective through December 31, 2022. The Company is currently evaluating the impact that adopting this new accounting standard will have on the consolidated financial statements.
Revenue Recognition	The Company recognizes revenue from contracts with customers in accordance with ASC Topic 606, Revenue from Contracts with Customers . The core principle requires an entity to recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration it expects to be entitled to receive in exchange for those goods or services recognized as performance obligations are satisfied. The majority of the Company's revenue-generating transactions are not subject to ASC Topic 606, including revenue generated from financial instruments, such as loans, letters of credit, derivatives and investment securities, as well as revenue related to mortgage servicing activities, as these activities are subject to other GAAP and discussed elsewhere within Item 8. Financial Statements and Supplementary Data, "Note 1. Nature of Operations and Summary of Significant Accounting Policies" in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020. Descriptions of the Company's revenue-generating activities that are within the scope of ASC Topic 606, which are presented in the consolidated income statements as components of noninterest income, are as follows: Service charges and fees on deposit accounts. Service charges on deposit accounts are earned for account maintenance and overdraft, wire and treasury management services. Revenue is recognized at the time the services are performed and is included in service charges and other fees within noninterest income on the consolidated statements of income. Interchange and merchant services income. Interchange and merchant services income are earned from credit and debit card payment processing through card association networks, merchant services and other card related services. Fees for these services are primarily based on interchange rates set by the networks and transaction volumes and are recognized as transactions are processed and settled with networks on behalf of card holders. These fees are presented net of direct expenses, including reward costs, associated with credit and debit card interchange income in service charges and other fees which are included in noninterest income on the consolidated statements of income. Wealth management and trust fee income. Wealth management and trust fees are earned for asset management, custody and recordkeeping, investment advisory and administrative services. Revenue is recognized as the services are performed. Brokerage charges are recorded as a net reduction in wealth management fees which are included in noninterest income on the consolidated statements of income. Other noninterest income. Other noninterest income primarily includes such items as letter of credit fees, gains on sale of loans held for sale and servicing fees, none of which are subject to the requirements of ASC Topic 606.

Nature of Operations and Summ_3

Nature of Operations and Summary of Significant Policies (Tables)	3 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of the composition of the loan portfolio by internal risk rating	Credit Quality Credit Quality Indicators Pass Commercial loans within this category are not adversely rated, current as to principal and interest, and are otherwise in compliance with the contractual terms of the loan agreement. Management believes there is a low likelihood of loss related to loans in this category. Special Mention Commercial loans within this category have potential weaknesses that deserve management's close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or in the Company's credit position at some future date. Special mention assets are not adversely classified and do not expose the Company to sufficient risk to warrant an adverse classification. Substandard Commercial loans within this category are inadequately protected by the current sound worth and paying capacity of the borrower or of the collateral pledged, if any. Assets so classified must have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans in this category are assigned a workout loan officer to closely monitor the relationship. Doubtful Commercial loans within this category are considered uncollectible and of such little value that their continuance as bankable assets is not warranted. This classification does not mean that the asset has absolutely no recovery or salvage value, but rather that it is not practical or desirable to defer writing off this basically worthless asset even though partial recovery may be effected in the future. Term loans Fiscal Year to Date Fiscal Year 2021 2020 2019 2018 2017 Prior to 2017 Revolving Loans Revolving Loans Total (dollars in thousands) Construction and development Pass $ 86,339 $ 160,884 $ 108,053 $ 30,830 $ 2,570 $ 824 $ 63,584 $ — $ 453,084 Special Mention 3,686 — 200 — — — — — 3,886 Substandard 11,322 33 — 12,746 — — 1,364 — 25,465 Doubtful — — 27 — — — — — 27 Total construction and development $ 101,347 $ 160,917 $ 108,280 $ 43,576 $ 2,570 $ 824 $ 64,948 $ — $ 482,462 Owner-occupied CRE Pass $ 104,322 $ 372,920 $ 227,194 $ 117,287 $ 164,280 $ 185,366 $ 51,397 $ 59 $ 1,222,825 Special Mention 465 1,853 2,170 6,651 8,481 8,032 332 — 27,984 Substandard 4,358 4,609 4,643 18,257 11,704 6,447 — — 50,018 Doubtful — — 3,190 — — — — — 3,190 Total owner-occupied CRE $ 109,145 $ 379,382 $ 237,197 $ 142,195 $ 184,465 $ 199,845 $ 51,729 $ 59 $ 1,304,017 Non-owner-occupied CRE Pass $ 161,105 $ 423,025 $ 360,220 $ 348,757 $ 382,487 $ 334,667 $ 44,898 $ — $ 2,055,159 Special Mention 18,991 1,555 35,322 77,164 15,448 16,874 — — 165,354 Substandard 14,418 64,261 15,527 41,830 — 7,758 35,459 — 179,253 Doubtful — — — — — — — — — Total non-owner-occupied CRE $ 194,514 $ 488,841 $ 411,069 $ 467,751 $ 397,935 $ 359,299 $ 80,357 $ — $ 2,399,766 Multifamily residential real estate Pass $ 72,043 $ 100,793 $ 102,328 $ 71,541 $ 16,889 $ 56,216 $ 248 $ — $ 420,058 Special Mention 256 — 2,629 20,686 46 107 21,200 — 44,924 Substandard — 7,311 — — 487 334 — — 8,132 Doubtful — — — — — — — — — Total multifamily residential real estate $ 72,299 $ 108,104 $ 104,957 $ 92,227 $ 17,422 $ 56,657 $ 21,448 $ — $ 473,114 Total commercial real estate Pass $ 423,809 $ 1,057,622 $ 797,795 $ 568,415 $ 566,226 $ 577,073 $ 160,127 $ 59 $ 4,151,126 Special Mention 23,398 3,408 40,321 104,501 23,975 25,013 21,532 — 242,148 Substandard 30,098 76,214 20,170 72,833 12,191 14,539 36,823 — 262,868 Doubtful — — 3,217 — — — — — 3,217 Total commercial real estate $ 477,305 $ 1,137,244 $ 861,503 $ 745,749 $ 602,392 $ 616,625 $ 218,482 $ 59 $ 4,659,359 Term loans Fiscal Year to Date Fiscal Year 2021 2020 2019 2018 2017 Prior to 2017 Revolving Loans Revolving Loans Total (dollars in thousands) Agriculture Pass $ 56,160 $ 222,029 $ 105,591 $ 85,249 $ 82,726 $ 62,253 $ 460,060 $ — $ 1,074,068 Special Mention 21,040 29,166 7,402 13,400 23,817 4,511 49,451 — 148,787 Substandard 11,412 36,842 15,034 41,653 39,723 8,121 114,838 — 267,623 Doubtful 1,595 49 754 22,230 1,446 — 3,475 — 29,549 Total agriculture $ 90,207 $ 288,086 $ 128,781 $ 162,532 $ 147,712 $ 74,885 $ 627,824 $ — $ 1,520,027 Commercial non-real estate Pass $ 28,084 $ 827,457 $ 195,666 $ 63,526 $ 52,661 $ 43,956 $ 573,735 $ 8 $ 1,785,093 Special Mention 6,500 21,521 2,812 1,714 2,576 864 19,391 — 55,378 Substandard 7,950 20,120 12,992 4,561 255 1,395 32,619 — 79,892 Doubtful — 390 52 84 — 4,269 5,159 — 9,954 Total commercial non-real estate $ 42,534 $ 869,488 $ 211,522 $ 69,885 $ 55,492 $ 50,484 $ 630,904 $ 8 $ 1,930,317 Residential real estate ¹ Pass $ 48,697 $ 213,698 $ 86,203 $ 52,442 $ 31,231 $ 119,770 $ 138,017 $ 282 $ 690,340 Special Mention 297 825 341 303 304 998 220 — 3,288 Substandard 279 1,545 2,828 1,363 421 6,083 1,937 — 14,456 Doubtful — — — — — 2 — — 2 Total residential real estate $ 49,273 $ 216,068 $ 89,372 $ 54,108 $ 31,956 $ 126,853 $ 140,174 $ 282 $ 708,086 Consumer and other ¹ Pass $ 31,451 $ 22,536 $ 16,856 $ 2,898 $ 1,220 $ 1,370 $ 12,058 $ — $ 88,389 Special Mention 9 — — — — 12 3 — 24 Substandard 6 6 18 2 10 8 35 — 85 Doubtful — — — 1 — — — — 1 Total consumer and other $ 31,466 $ 22,542 $ 16,874 $ 2,901 $ 1,230 $ 1,390 $ 12,096 $ — $ 88,499 Total loans Pass $ 588,201 $ 2,343,342 $ 1,202,111 $ 772,530 $ 734,064 $ 804,422 $ 1,343,997 $ 349 $ 7,789,016 Special Mention 51,244 54,920 50,876 119,918 50,672 31,398 90,597 — 449,625 Substandard 49,745 134,727 51,042 120,412 52,600 30,146 186,252 — 624,924 Doubtful 1,595 439 4,023 22,315 1,446 4,271 8,634 — 42,723 Total loans $ 690,785 $ 2,533,428 $ 1,308,052 $ 1,035,175 $ 838,782 $ 870,237 $ 1,629,480 $ 349 $ 8,906,288 1 The Company generally does not risk rate residential real estate or consumer and other loans unless a default event such as a bankruptcy or extended nonperformance takes place. Alternatively, standard credit scoring systems are used to assess credit risks of residential real estate and consumer and other loans. The following table presents the composition of the loan portfolio by internally assigned grade as of September 30, 2020. This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value under the fair value option of $655.2 million at September 30, 2020. As of September 30, 2020 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer and Other ¹ Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,062,814 $ 968,875 $ 1,851,323 $ 806,436 $ 99,632 $ 7,789,080 Watchlist 577,399 265,714 94,401 6,972 709 945,195 Substandard 229,467 348,910 94,316 13,173 93 685,959 Doubtful 3,323 11,540 11,623 1,473 4 27,963 Loss — — — — — — Ending balance 4,873,003 1,595,039 2,051,663 828,054 100,438 9,448,197 1 The Company generally does not risk rate residential real estate or consumer and other loans unless a default event such as a bankruptcy or extended nonperformance takes place. Alternatively, standard credit scoring systems are used to assess credit risks of residential real estate and consumer and other loans.
Schedule of loans receivable	The following table describes the Company’s eight loan portfolio pools, which is the level at which it develops and documents a systematic methodology to determine the allowance for credit losses. Loan Segment Composition Collateral Primary Source of Repayment Key Risk Characteristics Construction and development 1 Commercial and residential construction loans Secured by commercial and residential real estate Cash flows Industry and geography of borrower's business, purpose of the loan, repayment sources, borrower's capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Owner-occupied CRE Small and middle market businesses Secured by commercial real estate Non-owner-occupied CRE Multifamily residential real estate Agriculture Agri-business operating and real estate loans Secured by operating assets, agricultural real estate, and guarantees of owners Cash flows Geography of the borrower's operations, commodity type and prices and weather patterns, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Commercial non-real estate Small and middle market businesses and loans made to public sector Secured by business assets and guarantees of owners Cash flows Industry and geography of the borrower's business, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Residential real estate Residential mortgages and home equity loans and lines Secured by residential real estate Borrower's income Borrower's capacity and willingness to repay, unemployment rates and other economic factors, and customer repayment history Consumer and other Consumer loans and all other loan relationships that do not fit within categories above, including consumer and commercial credit cards and consumer deposit account overdrafts Secured by automobiles, unsecured 1 Residential real estate construction loans are included in the construction and development segment until construction is completed, after which the loan is moved to the residential real estate loan segment. The following table presents the composition of loans at amortized cost as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 Total Loans Less: Fair Value Option Loans Less: Guaranteed Loans ¹ Loans at Amortized Cost Total Loans ² Less: Fair Value Option Loans Less: Guaranteed Loans ¹ Loans at Amortized Cost (dollars in thousands) Construction and development $ 482,462 $ — $ — $ 482,462 $ 509,644 $ — $ — $ 509,644 Owner-occupied CRE 1,411,558 107,541 47,808 1,256,209 1,417,394 109,097 48,468 1,259,829 Non-owner-occupied CRE 2,660,682 260,916 27,168 2,372,598 2,894,380 283,266 27,402 2,583,712 Multifamily residential real estate 476,159 3,045 — 473,114 533,983 3,847 — 530,136 Total commercial real estate 5,030,861 371,502 74,976 4,584,383 5,355,401 396,210 75,870 4,883,321 Agriculture 1,635,952 115,925 39,426 1,480,601 1,722,696 129,041 42,353 1,551,302 Commercial non-real estate 2,054,478 124,161 715,163 1,215,154 2,165,038 129,934 744,371 1,290,733 Residential real estate ³ 708,086 — 294 707,792 730,812 — 290 730,522 Consumer and other ⁴ 88,499 — — 88,499 102,195 — 102,195 Total $ 9,517,876 $ 611,588 $ 829,859 $ 8,076,429 $ 10,076,142 $ 655,185 $ 862,884 $ 8,558,073 1 Includes loans guaranteed by agencies of the U.S. government. 2 As a part of the adoption of CECL, loan segments are presented based on amortized cost, which includes unpaid principal balance, unamortized discount on acquired loans, and unearned net deferred fees and costs. For additional information on September 30, 2020 loan segment balances, see Note 2. 3 Includes residential real estate loans held for sale of $11.6 million and $12.4 million at December 31, 2020 and September 30, 2020, respectively, recorded at the lower of cost or fair value.. 4 Other loans primarily include consumer and commercial credit cards, customer deposit account overdrafts and loans in process.

New Accounting Standards (Table

New Accounting Standards (Tables)	3 Months Ended
	Dec. 31, 2020
Accounting Changes and Error Corrections [Abstract]
Accounting Standards Update and Change in Accounting Principle	The following table presents the composition of loans and allowance by portfolio segment as of September 30, 2020, as adjusted at September 30, 2020 and October 1, 2020. Reported Balance September 30, Reclassifications ¹ Unamortized Discounts, Unearned Net Deferred Fees and Net Loans in Process Included in Amortized Cost ² Adjusted Balance September 30, Adoption of ASU 2016-13, as amended ³ Adjusted Balance October 1, 2020 (dollars in thousands) Loans: Construction and development n/a ⁴ $ 512,539 $ (2,895) $ 509,644 $ — $ 509,644 Owner-occupied CRE n/a ⁴ 1,420,061 (2,667) 1,417,394 36 1,417,430 Non-owner-occupied CRE n/a ⁴ 2,902,612 (8,232) 2,894,380 1,497 2,895,877 Multifamily residential real estate n/a ⁴ 536,828 (2,845) 533,983 (8) 533,975 Total commercial real estate 5,274,941 (5,274,941) — — — — Agriculture 1,724,350 — (1,654) 1,722,696 55 1,722,751 Commercial non-real estate 2,181,656 — (16,618) 2,165,038 (85) 2,164,953 Residential real estate 830,102 (97,099) (2,191) 730,812 23 730,835 Consumer and other — 100,553 1,642 102,195 (20) 102,175 Consumer 63,206 (63,206) — — — — Other 37,347 (37,347) — — — — Ending balance 10,111,602 — (35,460) 10,076,142 1,498 10,077,640 Less: Unamortized discount (8,215) — 8,215 — — — Unearned net deferred fees and (27,245) — 27,245 — — — Total $ 10,076,142 $ — $ — $ 10,076,142 $ 1,498 $ 10,077,640 Allowance: Construction and development n/a ⁴ $ (7,012) $ — $ (7,012) $ (11,963) $ (18,975) Owner-occupied CRE n/a ⁴ (20,530) — (20,530) (4,298) (24,828) Non-owner-occupied CRE n/a ⁴ (50,965) — (50,965) (98,986) (149,951) Multifamily residential real estate n/a ⁴ (6,726) — (6,726) (2,681) (9,407) Total commercial real estate (84,496) 84,496 — — — — Agriculture (27,018) — — (27,018) (24,360) (51,378) Commercial non-real estate (27,599) — — (27,599) (32,938) (60,537) Residential real estate (8,202) 737 — (7,465) (2,595) (10,060) Consumer and other (2,572) — — (2,572) 532 (2,040) Total $ (149,887) $ — $ — $ (149,887) $ (177,289) $ (327,176) 1 Reclassifications made from reported loan and related allowance segments to align with the eight loan portfolio segments established for adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, to estimate credit losses. 2 Unamortized discount on acquired loans, unearned net deferred fees and costs and net loans in process to related were assigned to appropriate loan portfolio segment to present loan categories at amortized cost. 3 Discounts on previously acquired loans and Day 1 impact of adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, were transferred to allowance for credit losses as a part of CECL adoption. 4 Balance for this segment is included in total commercial real estate for September 30, 2020.

Securities Available for Sale (

Securities Available for Sale (Tables)	3 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of amortized cost and fair value of investments by contractual maturity	The amortized cost and approximate fair value of investments in securities, all of which are classified as available for sale according to management’s intent, are summarized as follows. Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated (dollars in thousands) As of December 31, 2020 U.S. Treasury securities $ 24,991 $ 23 $ — $ 25,014 U.S. Agency securities 24,975 — (272) 24,703 Mortgage-backed securities: Government National Mortgage Association 424,756 10,220 (102) 434,874 Federal Home Loan Mortgage Corporation 769,254 17,187 (65) 786,376 Federal National Mortgage Association 455,651 7,301 (206) 462,746 Small Business Assistance Program 264,798 7,829 (192) 272,435 States and political subdivision securities 51,120 1,297 — 52,417 Other 1,006 44 — 1,050 Total $ 2,016,551 $ 43,901 $ (837) $ 2,059,615 Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated (dollars in thousands) As of September 30, 2020 U.S. Treasury securities $ 49,924 $ 228 $ — $ 50,152 U.S. Agency securities 24,974 86 — 25,060 Mortgage-backed securities: Government National Mortgage Association 485,689 11,481 (43) 497,127 Federal Home Loan Mortgage Corporation 578,650 18,919 (9) 597,560 Federal National Mortgage Association 287,842 7,788 (16) 295,614 Small Business Assistance Program 244,653 7,884 (58) 252,479 States and political subdivision securities 54,224 1,356 — 55,580 Other 1,006 48 — 1,054 Total $ 1,726,962 $ 47,790 $ (126) $ 1,774,626 The amortized cost and approximate fair value of debt securities available for sale as of December 31, 2020 and September 30, 2020, by contractual maturity, are shown below. Maturities of mortgage-backed securities may differ from contractual maturities because the mortgages underlying the securities may be called or repaid without penalty. December 31, 2020 September 30, 2020 Amortized Estimated Amortized Estimated (dollars in thousands) Due in one year or less $ 42,973 $ 43,103 $ 67,131 $ 67,456 Due after one year through five years 48,047 48,499 51,779 52,694 Due after five years through ten years 10,066 10,532 10,212 10,642 Due after ten years — — — — 101,086 102,134 129,122 130,792 Mortgage-backed securities 1,914,459 1,956,431 1,596,834 1,642,780 Securities without contractual maturities 1,006 1,050 1,006 1,054 Total $ 2,016,551 $ 2,059,615 $ 1,726,962 $ 1,774,626
Schedule of gross unrealized losses on investments	The following table presents the Company’s gross unrealized losses and approximate fair value in investments, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position. Less than 12 months 12 months or more Total Estimated Unrealized Estimated Unrealized Estimated Unrealized (dollars in thousands) As of December 31, 2020 U.S. Agency securities $ 24,703 $ (272) $ — $ — $ 24,703 $ (272) Mortgage-backed securities 146,799 (553) 8,388 (12) 155,187 (565) Total $ 171,502 $ (825) $ 8,388 $ (12) $ 179,890 $ (837) Less than 12 months 12 months or more Total Estimated Unrealized Estimated Unrealized Estimated Unrealized (dollars in thousands) As of September 30, 2020 U.S. Agency securities $ — $ — $ — $ — $ — $ — Mortgage-backed securities 71,547 (103) 27,897 (23) 99,444 (126) Total $ 71,547 $ (103) $ 27,897 $ (23) $ 99,444 $ (126)

Loans and Allowance for Credi_2

Loans and Allowance for Credit Losses (Tables)	3 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Schedule of loans receivable	The following table describes the Company’s eight loan portfolio pools, which is the level at which it develops and documents a systematic methodology to determine the allowance for credit losses. Loan Segment Composition Collateral Primary Source of Repayment Key Risk Characteristics Construction and development 1 Commercial and residential construction loans Secured by commercial and residential real estate Cash flows Industry and geography of borrower's business, purpose of the loan, repayment sources, borrower's capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Owner-occupied CRE Small and middle market businesses Secured by commercial real estate Non-owner-occupied CRE Multifamily residential real estate Agriculture Agri-business operating and real estate loans Secured by operating assets, agricultural real estate, and guarantees of owners Cash flows Geography of the borrower's operations, commodity type and prices and weather patterns, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Commercial non-real estate Small and middle market businesses and loans made to public sector Secured by business assets and guarantees of owners Cash flows Industry and geography of the borrower's business, purpose of the loan, repayment sources, borrower's debt capacity and financial performance, loan covenants, guarantees and nature of pledged collateral Residential real estate Residential mortgages and home equity loans and lines Secured by residential real estate Borrower's income Borrower's capacity and willingness to repay, unemployment rates and other economic factors, and customer repayment history Consumer and other Consumer loans and all other loan relationships that do not fit within categories above, including consumer and commercial credit cards and consumer deposit account overdrafts Secured by automobiles, unsecured 1 Residential real estate construction loans are included in the construction and development segment until construction is completed, after which the loan is moved to the residential real estate loan segment. The following table presents the composition of loans at amortized cost as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 Total Loans Less: Fair Value Option Loans Less: Guaranteed Loans ¹ Loans at Amortized Cost Total Loans ² Less: Fair Value Option Loans Less: Guaranteed Loans ¹ Loans at Amortized Cost (dollars in thousands) Construction and development $ 482,462 $ — $ — $ 482,462 $ 509,644 $ — $ — $ 509,644 Owner-occupied CRE 1,411,558 107,541 47,808 1,256,209 1,417,394 109,097 48,468 1,259,829 Non-owner-occupied CRE 2,660,682 260,916 27,168 2,372,598 2,894,380 283,266 27,402 2,583,712 Multifamily residential real estate 476,159 3,045 — 473,114 533,983 3,847 — 530,136 Total commercial real estate 5,030,861 371,502 74,976 4,584,383 5,355,401 396,210 75,870 4,883,321 Agriculture 1,635,952 115,925 39,426 1,480,601 1,722,696 129,041 42,353 1,551,302 Commercial non-real estate 2,054,478 124,161 715,163 1,215,154 2,165,038 129,934 744,371 1,290,733 Residential real estate ³ 708,086 — 294 707,792 730,812 — 290 730,522 Consumer and other ⁴ 88,499 — — 88,499 102,195 — 102,195 Total $ 9,517,876 $ 611,588 $ 829,859 $ 8,076,429 $ 10,076,142 $ 655,185 $ 862,884 $ 8,558,073 1 Includes loans guaranteed by agencies of the U.S. government. 2 As a part of the adoption of CECL, loan segments are presented based on amortized cost, which includes unpaid principal balance, unamortized discount on acquired loans, and unearned net deferred fees and costs. For additional information on September 30, 2020 loan segment balances, see Note 2. 3 Includes residential real estate loans held for sale of $11.6 million and $12.4 million at December 31, 2020 and September 30, 2020, respectively, recorded at the lower of cost or fair value.. 4 Other loans primarily include consumer and commercial credit cards, customer deposit account overdrafts and loans in process.
Schedule of the Company's nonaccrual loans	The following table presents the Company’s past due and nonaccrual loans at amortized cost as of December 31, 2020. This table excludes loans measured at fair value under the fair value option of $611.6 million at December 31, 2020. Loans greater than 90 days past due and still accruing interest as of December 31, 2020 were nominal. As of December 31, 2020 Current or Less Than 30 Days Past Due 30-89 Days Past Due Nonaccrual Total (dollars in thousands) Construction and development $ 468,025 $ 180 $ 14,257 $ 482,462 Owner-occupied CRE 1,286,830 411 16,776 1,304,017 Non-owner-occupied CRE 2,346,904 16,097 36,765 2,399,766 Multifamily residential real estate 472,675 439 — 473,114 Total commercial real estate 4,574,434 17,127 67,798 4,659,359 Agriculture 1,322,075 12,319 185,633 1,520,027 Commercial non-real estate 1,909,610 3,210 17,497 1,930,317 Residential real estate 698,146 3,166 6,774 708,086 Consumer and other 88,228 152 70 88,450 Total $ 8,592,493 $ 35,974 $ 277,772 $ 8,906,239 The following table presents the Company’s past due loans at September 30, 2020. This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value under the fair value option of $655.2 million at September 30, 2020. Current or Less Than 30 Days Past Due 30-89 Days Past Due Nonaccrual Total (dollars in thousands) As of September 30, 2020 Commercial real estate $ 4,790,963 $ 8,894 $ 73,146 $ 4,873,003 Agriculture 1,317,377 60,020 217,642 1,595,039 Commercial non-real estate 2,021,308 3,512 26,843 2,051,663 Residential real estate 821,154 2,459 4,441 828,054 Consumer and other 100,319 45 74 100,438 Ending balance $ 9,051,121 $ 74,930 $ 322,146 $ 9,448,197 The following table provides additional information on nonaccrual loans for the three months ended December 31, 2020. There were no loans greater than 90 days past due and still accruing interest as of September 30, 2020. Three Months Ended December 31, 2020 Nonaccrual Nonaccrual Nonaccrual Loans with No Related ACL Interest Income Recognized on Nonaccrual Loans Accrued Interest Written Off on Nonaccrual Loans (dollars in thousands) Construction and development n/a ¹ $ 14,257 $ — $ — $ 110 Owner-occupied CRE n/a ¹ 16,776 8,036 — 13 Non-owner-occupied CRE n/a ¹ 36,765 11,686 — 1,717 Multifamily residential real estate n/a ¹ — — — — Total commercial real estate $ 73,146 67,798 19,722 — 1,840 Agriculture 217,642 185,633 154,508 — 382 Commercial non-real estate 26,843 17,497 7,711 — 2 Residential real estate 4,441 6,774 — — 25 Consumer and other 74 70 — — 1 Total $ 322,146 $ 277,772 $ 181,941 $ — $ 2,250 1 Balance for this segment is included in total commercial real estate for September 30, 2020.
Schedule of the composition of the loan portfolio by internal risk rating	Credit Quality Credit Quality Indicators Pass Commercial loans within this category are not adversely rated, current as to principal and interest, and are otherwise in compliance with the contractual terms of the loan agreement. Management believes there is a low likelihood of loss related to loans in this category. Special Mention Commercial loans within this category have potential weaknesses that deserve management's close attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the loan or in the Company's credit position at some future date. Special mention assets are not adversely classified and do not expose the Company to sufficient risk to warrant an adverse classification. Substandard Commercial loans within this category are inadequately protected by the current sound worth and paying capacity of the borrower or of the collateral pledged, if any. Assets so classified must have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Loans in this category are assigned a workout loan officer to closely monitor the relationship. Doubtful Commercial loans within this category are considered uncollectible and of such little value that their continuance as bankable assets is not warranted. This classification does not mean that the asset has absolutely no recovery or salvage value, but rather that it is not practical or desirable to defer writing off this basically worthless asset even though partial recovery may be effected in the future. Term loans Fiscal Year to Date Fiscal Year 2021 2020 2019 2018 2017 Prior to 2017 Revolving Loans Revolving Loans Total (dollars in thousands) Construction and development Pass $ 86,339 $ 160,884 $ 108,053 $ 30,830 $ 2,570 $ 824 $ 63,584 $ — $ 453,084 Special Mention 3,686 — 200 — — — — — 3,886 Substandard 11,322 33 — 12,746 — — 1,364 — 25,465 Doubtful — — 27 — — — — — 27 Total construction and development $ 101,347 $ 160,917 $ 108,280 $ 43,576 $ 2,570 $ 824 $ 64,948 $ — $ 482,462 Owner-occupied CRE Pass $ 104,322 $ 372,920 $ 227,194 $ 117,287 $ 164,280 $ 185,366 $ 51,397 $ 59 $ 1,222,825 Special Mention 465 1,853 2,170 6,651 8,481 8,032 332 — 27,984 Substandard 4,358 4,609 4,643 18,257 11,704 6,447 — — 50,018 Doubtful — — 3,190 — — — — — 3,190 Total owner-occupied CRE $ 109,145 $ 379,382 $ 237,197 $ 142,195 $ 184,465 $ 199,845 $ 51,729 $ 59 $ 1,304,017 Non-owner-occupied CRE Pass $ 161,105 $ 423,025 $ 360,220 $ 348,757 $ 382,487 $ 334,667 $ 44,898 $ — $ 2,055,159 Special Mention 18,991 1,555 35,322 77,164 15,448 16,874 — — 165,354 Substandard 14,418 64,261 15,527 41,830 — 7,758 35,459 — 179,253 Doubtful — — — — — — — — — Total non-owner-occupied CRE $ 194,514 $ 488,841 $ 411,069 $ 467,751 $ 397,935 $ 359,299 $ 80,357 $ — $ 2,399,766 Multifamily residential real estate Pass $ 72,043 $ 100,793 $ 102,328 $ 71,541 $ 16,889 $ 56,216 $ 248 $ — $ 420,058 Special Mention 256 — 2,629 20,686 46 107 21,200 — 44,924 Substandard — 7,311 — — 487 334 — — 8,132 Doubtful — — — — — — — — — Total multifamily residential real estate $ 72,299 $ 108,104 $ 104,957 $ 92,227 $ 17,422 $ 56,657 $ 21,448 $ — $ 473,114 Total commercial real estate Pass $ 423,809 $ 1,057,622 $ 797,795 $ 568,415 $ 566,226 $ 577,073 $ 160,127 $ 59 $ 4,151,126 Special Mention 23,398 3,408 40,321 104,501 23,975 25,013 21,532 — 242,148 Substandard 30,098 76,214 20,170 72,833 12,191 14,539 36,823 — 262,868 Doubtful — — 3,217 — — — — — 3,217 Total commercial real estate $ 477,305 $ 1,137,244 $ 861,503 $ 745,749 $ 602,392 $ 616,625 $ 218,482 $ 59 $ 4,659,359 Term loans Fiscal Year to Date Fiscal Year 2021 2020 2019 2018 2017 Prior to 2017 Revolving Loans Revolving Loans Total (dollars in thousands) Agriculture Pass $ 56,160 $ 222,029 $ 105,591 $ 85,249 $ 82,726 $ 62,253 $ 460,060 $ — $ 1,074,068 Special Mention 21,040 29,166 7,402 13,400 23,817 4,511 49,451 — 148,787 Substandard 11,412 36,842 15,034 41,653 39,723 8,121 114,838 — 267,623 Doubtful 1,595 49 754 22,230 1,446 — 3,475 — 29,549 Total agriculture $ 90,207 $ 288,086 $ 128,781 $ 162,532 $ 147,712 $ 74,885 $ 627,824 $ — $ 1,520,027 Commercial non-real estate Pass $ 28,084 $ 827,457 $ 195,666 $ 63,526 $ 52,661 $ 43,956 $ 573,735 $ 8 $ 1,785,093 Special Mention 6,500 21,521 2,812 1,714 2,576 864 19,391 — 55,378 Substandard 7,950 20,120 12,992 4,561 255 1,395 32,619 — 79,892 Doubtful — 390 52 84 — 4,269 5,159 — 9,954 Total commercial non-real estate $ 42,534 $ 869,488 $ 211,522 $ 69,885 $ 55,492 $ 50,484 $ 630,904 $ 8 $ 1,930,317 Residential real estate ¹ Pass $ 48,697 $ 213,698 $ 86,203 $ 52,442 $ 31,231 $ 119,770 $ 138,017 $ 282 $ 690,340 Special Mention 297 825 341 303 304 998 220 — 3,288 Substandard 279 1,545 2,828 1,363 421 6,083 1,937 — 14,456 Doubtful — — — — — 2 — — 2 Total residential real estate $ 49,273 $ 216,068 $ 89,372 $ 54,108 $ 31,956 $ 126,853 $ 140,174 $ 282 $ 708,086 Consumer and other ¹ Pass $ 31,451 $ 22,536 $ 16,856 $ 2,898 $ 1,220 $ 1,370 $ 12,058 $ — $ 88,389 Special Mention 9 — — — — 12 3 — 24 Substandard 6 6 18 2 10 8 35 — 85 Doubtful — — — 1 — — — — 1 Total consumer and other $ 31,466 $ 22,542 $ 16,874 $ 2,901 $ 1,230 $ 1,390 $ 12,096 $ — $ 88,499 Total loans Pass $ 588,201 $ 2,343,342 $ 1,202,111 $ 772,530 $ 734,064 $ 804,422 $ 1,343,997 $ 349 $ 7,789,016 Special Mention 51,244 54,920 50,876 119,918 50,672 31,398 90,597 — 449,625 Substandard 49,745 134,727 51,042 120,412 52,600 30,146 186,252 — 624,924 Doubtful 1,595 439 4,023 22,315 1,446 4,271 8,634 — 42,723 Total loans $ 690,785 $ 2,533,428 $ 1,308,052 $ 1,035,175 $ 838,782 $ 870,237 $ 1,629,480 $ 349 $ 8,906,288 1 The Company generally does not risk rate residential real estate or consumer and other loans unless a default event such as a bankruptcy or extended nonperformance takes place. Alternatively, standard credit scoring systems are used to assess credit risks of residential real estate and consumer and other loans. The following table presents the composition of the loan portfolio by internally assigned grade as of September 30, 2020. This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value under the fair value option of $655.2 million at September 30, 2020. As of September 30, 2020 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer and Other ¹ Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,062,814 $ 968,875 $ 1,851,323 $ 806,436 $ 99,632 $ 7,789,080 Watchlist 577,399 265,714 94,401 6,972 709 945,195 Substandard 229,467 348,910 94,316 13,173 93 685,959 Doubtful 3,323 11,540 11,623 1,473 4 27,963 Loss — — — — — — Ending balance 4,873,003 1,595,039 2,051,663 828,054 100,438 9,448,197 1 The Company generally does not risk rate residential real estate or consumer and other loans unless a default event such as a bankruptcy or extended nonperformance takes place. Alternatively, standard credit scoring systems are used to assess credit risks of residential real estate and consumer and other loans.
Schedule of impaired loans	The following table presents the Company’s impaired loans at September 30, 2020. This table excludes purchased credit impaired loans and loans measured at fair value under the fair value option. September 30, 2020 Recorded Investment Unpaid Principal Balance Related Allowance for Credit Losses Impaired loans: (dollars in thousands) With an allowance for credit losses recorded: Commercial real estate $ 111,121 $ 114,034 $ 25,087 Agriculture 53,052 55,145 8,151 Commercial non-real estate 39,821 47,571 7,822 Residential real estate 5,670 6,314 1,903 Consumer and other 98 109 30 Total impaired loans with an allowance for credit losses recorded 209,762 223,173 42,993 With no allowance for credit losses recorded: Commercial real estate 121,380 161,211 — Agriculture 308,734 332,272 — Commercial non-real estate 66,542 75,365 — Residential real estate 6,543 8,818 — Consumer and other — 108 — Total impaired loans with no allowance for credit losses recorded 503,199 577,774 — Total impaired loans $ 712,961 $ 800,947 $ 42,993 The following table presents the average recorded investment on impaired loans and interest income recognized on impaired loans for the three months ended December 31, 2019. Three Months Ended December 31, 2019 Average Recorded Investment Interest Income Recognized While on Impaired Status (dollars in thousands) Commercial real estate $ 73,422 $ 2,379 Agriculture 360,397 8,517 Commercial non-real estate 72,389 2,870 Residential real estate 9,013 266 Consumer 179 1 Total $ 515,400 $ 14,033
Schedule of total contractually required principal and interest	The following is a summary of changes in the accretable difference for all loans accounted for under ASC 310-30 during the three months ended December 31, 2019. Three Months Ended December 31, 2019 (dollars in thousands) Balance, beginning of period $ 26,047 Accretion (1,940) Reclassification (to) from nonaccretable difference (2,977) Balance, end of period $ 21,130
Summary of troubled debt restructurings on accruing and nonaccrual loans	The following table presents the amortized cost of the Company’s TDR balances as of December 31, 2020 and recorded value of TDR balances as of September 30, 2020. December 31, 2020 September 30, 2020 Accruing Nonaccrual Accruing Nonaccrual (dollars in thousands) Construction and development $ 1,364 $ 27 n/a ¹ n/a ¹ Owner-occupied CRE 5,590 — n/a ¹ n/a ¹ Non-owner-occupied CRE 12,203 11,637 n/a ¹ n/a ¹ Multifamily residential real estate — — n/a ¹ n/a ¹ Total commercial real estate 19,157 11,664 $ 23,215 $ 11,913 Agriculture 3,356 35,736 2,976 45,971 Commercial non real estate 8,304 5,096 8,734 4,803 Real estate 269 69 277 74 Consumer and other 2 27 3 31 Total $ 31,088 $ 52,592 $ 35,205 $ 62,792 1 Balance for this segment is included in total commercial real estate for September 30, 2020. TDRs are generally restructured through either a rate modification, term extension, payment modification or due to a bankruptcy. The following table presents a summary of all accruing loans restructured in TDRs for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Construction and development — $ — $ — n/a ¹ n/a ¹ n/a ¹ Owner-occupied CRE — — — n/a ¹ n/a ¹ n/a ¹ Non-owner-occupied CRE 1 10,640 10,640 n/a ¹ n/a ¹ n/a ¹ Multifamily residential real estate — — — n/a ¹ n/a ¹ n/a ¹ Total commercial real estate 1 10,640 10,640 — — — Agriculture 1 700 700 — — — Commercial non-real estate — — — 2 1,144 1,444 Residential real estate — — — — — — Consumer and other — — — — — — Total accruing 2 $ 11,340 $ 11,340 2 $ 1,144 $ 1,444 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — 1 Balance for this segment is included in total commercial real estate for September 30, 2020. The following table presents a summary of all nonaccruing loans restructured in TDRs for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Construction and development — $ — $ — n/a ¹ n/a ¹ n/a ¹ Owner-occupied CRE — — — n/a ¹ n/a ¹ n/a ¹ Non-owner-occupied CRE — — — n/a ¹ n/a ¹ n/a ¹ Multifamily residential real estate — — — n/a ¹ n/a ¹ n/a ¹ Total commercial real estate — — — 1 2,216 2,216 Agriculture 3 2,776 2,776 10 1,455 1,455 Commercial non-real estate 1 748 748 2 830 830 Residential real estate — — — — — — Consumer and other — — — — — — Total nonaccruing 4 $ 3,524 $ 3,524 13 $ 4,501 $ 4,501 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — 1 Balance for this segment is included in total commercial real estate for September 30, 2020. The following table presents loans that were modified as TDRs within the previous 12 months and for which there was a payment default or a charge-off for the three months ended December 31, 2020 and 2019, respectively. Three Months Ended December 31, 2020 2019 Number of Loans Recorded Investment Number of Loans Recorded Investment (dollars in thousands) Construction and development — $ — n/a ¹ n/a ¹ Owner-occupied CRE — — n/a ¹ n/a ¹ Non-owner-occupied CRE — — n/a ¹ n/a ¹ Multifamily residential real estate — — n/a ¹ n/a ¹ Total commercial real estate — — — $ — Agriculture — — 19 14,347 Commercial non-real estate 3 653 1 2,834 Residential real estate — — — — Consumer and other — — — — Total 3 $ 653 20 $ 17,181 1 Balance for this segment is included in total commercial real estate for September 30, 2020.
Summary of allowances for loan and lease losses	The following tables presents ACL activity by loan portfolio segment for the three months ended December 31, 2020. Three Months Ended December 31, 2020 Adjusted balance September 30, 2020 ¹ Adoption of ASU 2016-13, as amended Adjusted beginning balance, October 1, 2020 Charge-offs Recoveries (Reversal of) provision for credit losses on loans Ending balance, December 31, 2020 (dollars in thousands) Construction and development $ 7,012 $ 11,963 $ 18,975 $ (27) $ 268 $ (502) $ 18,714 Owner-occupied CRE 20,530 4,298 24,828 — — 258 25,086 Non-owner-occupied CRE 50,965 98,986 149,951 (28,269) 61 (992) 120,751 Multifamily residential real estate 6,726 2,681 9,407 — — 366 9,773 Total commercial real estate 85,233 117,928 203,161 (28,296) 329 (870) 174,324 Agriculture 27,018 24,360 51,378 (2,144) 1,734 (3,989) 46,979 Commercial non-real estate 27,599 32,938 60,537 (2,043) 245 17,216 75,955 Residential real estate 7,465 2,595 10,060 (96) 32 (324) 9,672 Consumer and other 2,572 (532) 2,040 (232) 113 (57) 1,864 Total $ 149,887 $ 177,289 $ 327,176 $ (32,811) $ 2,453 $ 11,976 $ 308,794 1 At September 30, 2020, the allowance balances were reclassified to align with the eight loan portfolio segments established for adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs. For additional information, see Note 2. The following table presents ACL activity by loan portfolio segment for the three months ended December 31, 2019. Three Months Ended December 31, 2019 Beginning balance, October 1, 2019 Charge-offs Recoveries Provision for credit losses on loans Impairment (improvement) of ASC 310-30 loans Ending balance, December 31, 2019 (dollars in thousands) Commercial real estate $ 16,827 $ (37) $ 120 $ 572 $ (20) $ 17,462 Agriculture 30,819 (4,606) 103 5,978 (265) 32,029 Commercial non-real estate 17,567 (1,481) 112 1,191 — 17,389 Residential real estate 4,095 (169) 164 192 338 4,620 Consumer and other 1,466 (373) 71 117 — 1,281 Total $ 70,774 $ (6,666) $ 570 $ 8,050 $ 53 $ 72,781

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of derivative positions, notional amounts and estimated fair values	The following table presents the notional amounts and gross fair values of all derivative assets and liabilities held by the Company as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 Notional Amount Gross Asset Gross Liability Notional Amount Gross Asset Gross Liability (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps - FVO loan portfolio Financial institution counterparties $ 562,359 $ — $ (54,568) $ 592,241 $ — $ (62,587) Interest rate swaps - Other Financial institution counterparties 708,872 — (1,516) 641,189 — (1,672) Customer counterparties 708,872 74,495 — 641,189 83,533 — Interest rate caps Financial institution counterparties 26,538 2 — 20,538 2 — Customer counterparties 26,538 — (2) 20,538 — (2) Risk participation agreements 82,111 — (22) 80,681 — (32) Mortgage loan commitments 79,738 322 — 92,278 — (96) Mortgage loan forward sale contracts 80,441 — (322) 94,084 96 — Total $ 2,275,469 $ 74,819 $ (56,430) $ 2,182,738 $ 83,631 $ (64,389)
Summary of offsetting assets	The following tables provide information on the Company's netting adjustments as of December 31, 2020 and September 30, 2020. Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of December 31, 2020 Total Derivative Assets $ 74,819 $ (4,321) $ 17,763 $ 88,261 Total Derivative Liabilities ¹ (56,430) 4,321 51,785 (324) 1 There was an additional $25.1 million of collateral held for initial margin with a Futures Clearing Merchant for clearing derivatives at December 31, 2020 and is included in other assets in the consolidated balance sheets. Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of September 30, 2020 Total Derivative Assets $ 83,631 $ (5,263) $ 20,012 $ 98,380 Total Derivative Liabilities ¹ (64,389) 5,263 59,028 (98) 1 There was an additional $22.9 million of collateral held for initial margin with a Futures Clearing Merchant for clearing derivatives at September 30, 2020 and is included in other assets in the consolidated balance sheets.
Summary of offsetting liabilities	The following tables provide information on the Company's netting adjustments as of December 31, 2020 and September 30, 2020. Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of December 31, 2020 Total Derivative Assets $ 74,819 $ (4,321) $ 17,763 $ 88,261 Total Derivative Liabilities ¹ (56,430) 4,321 51,785 (324) 1 There was an additional $25.1 million of collateral held for initial margin with a Futures Clearing Merchant for clearing derivatives at December 31, 2020 and is included in other assets in the consolidated balance sheets. Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of September 30, 2020 Total Derivative Assets $ 83,631 $ (5,263) $ 20,012 $ 98,380 Total Derivative Liabilities ¹ (64,389) 5,263 59,028 (98) 1 There was an additional $22.9 million of collateral held for initial margin with a Futures Clearing Merchant for clearing derivatives at September 30, 2020 and is included in other assets in the consolidated balance sheets.
Summary of effect of derivatives on consolidated statements of income	The effect of derivatives on the consolidated statements of income for the three months ended December 31, 2020 and 2019 was as follows. Amount of (Loss) Gain Recognized in Consolidated Statements of Income Three Months Ended December 31, Location of (Loss) Gain Recognized in Consolidated Statements of Income 2020 2019 (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps - FVO loan portfolio Derivative interest expense $ (3,393) $ (890) Interest rate swaps - FVO loan portfolio Change in fair value of FVO loans and related derivatives 8,570 12,809 Interest rate swaps and other derivatives Other derivative income 898 1,597 Mortgage loan commitments Other derivative income (418) 28 Mortgage loan forward sale contracts Other derivative income 418 (28)

Core Deposits and Other Intan_2

Core Deposits and Other Intangibles (Tables)	3 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of finite-lived intangible assets	The following table presents a summary of intangible assets subject to amortization as of December 31, 2020 and September 30, 2020. Core Deposit Intangible Customer Relationships Intangible Other Total (dollars in thousands) As of December 31, 2020 Gross carrying amount $ 7,339 $ 3,172 $ 538 $ 11,049 Accumulated amortization (4,499) (305) (341) (5,145) Net intangible assets $ 2,840 $ 2,867 $ 197 $ 5,904 As of September 30, 2020 Gross carrying amount $ 7,339 $ 3,172 $ 538 $ 11,049 Accumulated amortization (4,316) (244) (325) (4,885) Net intangible assets $ 3,023 $ 2,928 $ 213 $ 6,164
Schedule of estimated amortization expense of intangible assets	Estimated amortization expense of intangible assets in subsequent fiscal years is as follows. Fiscal year Amount (dollars in thousands) Remaining in 2021 $ 754 2022 929 2023 831 2024 742 2025 683 2026 and thereafter 1,965 Total $ 5,904

Leases (Tables)

Leases (Tables)	3 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Summary of ROU Assets and Liabilities	The following table summarizes the ROU asset and lease liability as of December 31, 2020 and September 30, 2020. December 31, 2020 September 30, 2020 (dollars in thousands) ROU asset $ 21,264 $ 22,709 Total lease liability 22,586 24,114 Weighted average remaining lease term 6.21 years 6.29 years Weighted average discount rate ¹ 1.82 % 1.83 % 1 The Company uses its incremental borrowing rate to calculate the present value of lease payments when the interest rate implicit in the lease is not disclosed.
Supplemental Cash Flow Information	The following table presents supplemental cash flow information related to leases for the three months ended December 31, 2020 and 2019: Three Months Ended December 31, 2020 2019 (dollars in thousands) Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows paid for operating leases $ 1,482 $ 1,410 Right-of-use assets obtained in exchange for lease liabilities: Operating leases $ 987 $ 624
Remaining Minimum Lease Payments	The following table presents a maturity analysis of the Company's operating lease liability as of December 31, 2020. Fiscal year Amount (dollars in thousands) Remaining in 2021 $ 4,383 2022 4,701 2023 4,149 2024 3,410 2025 2,469 2026 and thereafter 5,395 Total undiscounted lease payments 24,507 Less: Amounts representing interest (1,921) Lease liability $ 22,586

Securities Sold Under Agreeme_2

Securities Sold Under Agreements to Repurchase (Tables)	3 Months Ended
	Dec. 31, 2020
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Abstract]
Schedule of repurchases agreements	The following tables present the gross obligation by the class of collateral pledged and the remaining contractual maturity of the agreements at December 31, 2020 and September 30, 2020. December 31, 2020 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total (dollars in thousands) Repurchase agreements Mortgage-backed securities $ 80,355 $ — $ — $ — $ 80,355 Total repurchase agreements $ 80,355 $ — $ — $ — $ 80,355 September 30, 2020 Remaining Contractual Maturity of the Agreements Overnight and Continuous Up to 30 Days 30-90 Days Greater than 90 Days Total (dollars in thousands) Repurchase agreements Mortgage-backed securities $ 65,506 $ — $ — $ — $ 65,506 Total repurchase agreements $ 65,506 $ — $ — $ — $ 65,506

FHLB Advances and Other Borro_2

FHLB Advances and Other Borrowings (Tables)	3 Months Ended
	Dec. 31, 2020
Federal Home Loan Banks [Abstract]
Schedule of FHLB advances and other borrowings	FHLB advances and other borrowings consist of the following at December 31, 2020 and September 30, 2020. December 31, September 30, (dollars in thousands) Short-term borrowings: Fed funds purchased, matured in October 2020 $ — $ 75,000 Long-term borrowings: Notes payable to FHLB, interest rates from 2.76% to 2.88% and maturity dates from September 2022 to September 2024 collateralized by real estate loans 120,000 120,000 Total $ 120,000 $ 195,000
Schedule of FHLB advances and other borrowings by maturity date	As of December 31, 2020, FHLB advances and other borrowings are due or callable (whichever is earlier) in subsequent fiscal years as follows. Fiscal year Amount (dollars in thousands) Remaining in 2021 $ — 2022 30,000 2023 30,000 2024 60,000 2025 — 2026 and thereafter — Total $ 120,000

Subordinated Debentures and S_2

Subordinated Debentures and Subordinated Notes Payable (Tables)	3 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Summary of subordinated debentures and subordinated notes payable	Subordinated debentures and subordinated notes payable are summarized as follows. December 31, 2020 September 30, 2020 Amount Outstanding Common Shares Held in Other Assets Amount Outstanding Common Shares Held in Other Assets (dollars in thousands) Junior subordinated debentures payable to non-consolidated trusts GW Statutory Trust IV, variable rate of 2.85%, plus 3 month LIBOR $ 23,093 $ 693 $ 23,093 $ 693 GW Statutory Trust VI, variable rate of 1.48%, plus 3 month LIBOR 30,928 928 30,928 928 SSB Trust II, variable rate of 1.85%, plus 3 month LIBOR 2,062 62 2,062 62 HF Capital Trust III, variable rate of 3.35%, plus 3 month LIBOR 5,155 155 5,155 155 HF Capital Trust IV, variable rate of 3.10%, plus 3 month LIBOR 7,217 217 7,217 217 HF Capital Trust V, variable rate of 1.83%, plus 3 month LIBOR 5,310 310 5,310 310 HF Capital Trust VI, variable rate of 1.65%, plus 3 month LIBOR 2,155 155 2,155 155 Total junior subordinated debentures payable 75,920 $ 2,520 75,920 $ 2,520 Less: fair value adjustment ¹ (2,054) (2,088) Total junior subordinated debentures payable, net of fair value adjustment 73,866 73,832 Subordinated notes payable Fixed to floating rate effective August 2020, 3.150% plus 3 month LIBOR 35,000 35,000 Total subordinated debentures and subordinated notes payable $ 108,866 $ 108,832 1 Adjustment reflects the fair value adjustments related to the junior subordinated deferrable interest debentures assumed as part of the HF Financial acquisition.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of restricted share and performance-based stock award activity	The following is a summary of the Plans’ restricted share and performance-based stock award activity as of December 31, 2020 and September 30, 2020. The number of performance shares granted in the following table are reflected at the amount of achievement of the pre-established targets. December 31, 2020 September 30, 2020 Common Weighted-Average Grant Date Fair Value Common Weighted-Average Grant Date Fair Value Restricted Shares Restricted shares, beginning of fiscal year 249,180 $ 32.89 190,805 $ 37.20 Granted 152,028 17.30 147,282 30.68 Vested (79,093) 36.28 (84,316) 38.60 Forfeited (2,017) 28.89 (4,591) 36.18 Canceled — — — — Restricted shares, end of period 320,098 $ 24.67 249,180 $ 32.89 Vested, but not issuable at end of period 87,324 $ 29.32 62,992 $ 33.98 Performance Shares Performance shares, beginning of fiscal year 175,740 $ 33.56 173,332 $ 38.50 Granted 115,885 17.26 62,278 40.15 Vested (25,452) 41.07 (54,861) 39.43 Forfeited (11,904) 39.04 (5,009) 37.90 Canceled — — — — Performance shares, end of period 254,269 $ 25.12 175,740 $ 33.56 Vested, but not issuable at end of period 5,612 $ 18.00 5,612 $ 18.00

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of fair value measurements of assets and liabilities	The following table presents the fair value measurements of assets and liabilities recognized in the accompanying consolidated balance sheets measured at fair value on a recurring basis and the level within the fair value hierarchy in which the fair value measurements fall at December 31, 2020 and September 30, 2020. Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of December 31, 2020 U.S. Treasury securities $ 25,014 $ 25,014 $ — $ — U.S. Agency securities 24,703 24,703 — — Mortgage-backed securities 1,956,431 — 1,956,431 — States and political subdivision securities 52,417 — 48,751 3,666 Other 1,050 — 1,050 — Total securities available for sale $ 2,059,615 $ 49,717 $ 2,006,232 $ 3,666 Derivatives-assets $ 88,261 $ — $ 88,261 $ — Derivatives-liabilities 324 — 324 — Fair value loans 611,588 — 611,588 — Loan servicing rights 1,063 — — 1,063 Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of September 30, 2020 U.S. Treasury securities $ 50,152 $ 50,152 $ — $ — U.S. Agency securities 25,060 25,060 — — Mortgage-backed securities 1,642,780 — 1,642,780 — States and political subdivision securities 55,580 — 51,783 3,797 Other 1,054 — 1,054 — Total securities available for sale $ 1,774,626 $ 75,212 $ 1,695,617 $ 3,797 Derivatives-assets $ 98,380 $ — $ 98,380 $ — Derivatives-liabilities 98 — 98 — Fair value loans 655,185 — 655,185 — Loan servicing rights 1,303 — — 1,303
Schedule of changes in Level 3 financial instruments	The following table presents the changes in Level 3 assets and liabilities measured at fair value on a recurring basis for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 (dollars in thousands) Other securities available for sale Balance, beginning of period $ 3,797 $ 4,120 Additions — — Principal paydown (131) (134) Balance, end of period $ 3,666 $ 3,986 Loan servicing rights Balance, beginning of period $ 1,303 $ 2,255 Realized and unrealized loss ¹ (240) (201) Balance, end of period $ 1,063 $ 2,054 1 Realized and unrealized loss related to loan servicing rights are reported as a component of mortgage banking income, net on the consolidated statements of income.
Summary of mortgage loans held-for-sale, fair value measurement	The following table presents the fair value measurement of assets and liabilities measured at fair value on a nonrecurring basis and the level within the fair value hierarchy in which the fair value measurements fall at December 31, 2020 and September 30, 2020. Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of December 31, 2020 Other repossessed property $ 8,594 $ — $ — $ 8,594 Impaired loans 275,334 — — 275,334 Mortgage loans held for sale, at lower of cost or fair value 11,638 — 11,638 — Property held for sale 600 — — 600 As of September 30, 2020 Other repossessed property $ 17,991 $ — $ — $ 17,991 Impaired loans 669,968 — — 669,968 Mortgage loans held for sale, at lower of cost or fair value 12,371 — 12,371 — Property held for sale 600 — — 600
Summary of valuation techniques and significant unobservable inputs used to measure Level 3 fair value measurements	The valuation techniques and significant unobservable inputs used to measure Level 3 fair value measurements at December 31, 2020 were as follows. Fair Value of Assets / (Liabilities) at December 31, 2020 Valuation Unobservable Range Weighted (dollars in thousands) Other repossessed property $ 8,594 Appraisal value Collateral specific adjustment N/A N/A Impaired loans 275,334 Appraisal value Collateral specific adjustment N/A N/A Property held for sale 600 Appraisal value Collateral specific adjustment N/A N/A
Schedule of fair values for balance sheet instruments	Fair values for on-balance sheet instruments as of December 31, 2020 and September 30, 2020 are as follows. December 31, 2020 September 30, 2020 Level in Fair Value Hierarchy Carrying Amount Fair Carrying Amount Fair (dollars in thousands) Assets Cash and cash equivalents Level 1 $ 1,061,796 $ 1,061,796 $ 432,887 $ 432,887 Loans, net, excluding fair valued loans, loans held for sale and impaired loans ¹ Level 3 8,619,316 8,623,172 8,738,617 8,768,314 Liabilities Time deposits Level 2 1,078,580 1,082,378 1,282,978 1,287,814 FHLB advances and other borrowings Level 2 120,000 129,077 195,000 204,715 Securities sold under repurchase agreements Level 2 80,355 80,355 65,506 65,506 Subordinated debentures and subordinated notes payable Level 2 108,866 93,213 108,832 96,424 1 Includes $29.2 million and $29.0 million of net deferred loan fees at December 31, 2020 and September 30, 2020, respectively, of which carrying value approximates fair value.

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of basic and diluted earnings per share	The following information was used in the computation of basic and diluted earnings per share (EPS) for the three months ended December 31, 2020 and 2019. Three Months Ended December 31, 2020 2019 (dollars in thousands, except per share data) Net income $ 41,319 $ 43,274 Weighted average common shares outstanding 55,119,909 56,377,631 Dilutive effect of stock based compensation 127,434 80,336 Weighted average common shares outstanding for diluted earnings per share calculation 55,247,343 56,457,967 Basic earnings per share $ 0.75 $ 0.77 Diluted earnings per share $ 0.75 $ 0.77

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Noninterest Income	The following table presents total noninterest income segregated between contracts with customers within the scope of ASC Topic 606 and those within the scope of other GAAP Topics. The following additionally presents revenues from customers that are included within noninterest income. Three Months Ended December 31, 2020 2019 (dollars in thousands) Noninterest income Service charges and other fees $ 9,624 $ 11,409 Wealth management fees 3,029 2,964 Other 848 668 Noninterest income from contracts with customers within the scope of ASC Topic 606 13,501 15,041 Noninterest income within the scope of other GAAP Topics ¹ 647 692 Total noninterest income $ 14,148 $ 15,733 1 The Company presents out of scope noninterest income for the purpose of reconciling noninterest income amounts within the scope of ASC Topic 606 to noninterest income amounts presented on the Company's consolidated statements of income.

Nature of Operations and Summ_4

Nature of Operations and Summary of Significant Policies - Narrative (Details)	Jan. 27, 2021$ / shares	Dec. 31, 2020pool$ / shares	Dec. 31, 2019$ / shares
Dividends Payable [Line Items]
Fair value option, maturity period		5 years
Number of portfolio pools | pool		8
Common stock dividends declared (in dollars per share)		$ 0.01	$ 0.30
Minimum
Dividends Payable [Line Items]
Fair value option, maturity period		5 years
Maximum
Dividends Payable [Line Items]
Fair value option, maturity period		15 years
Subsequent event
Dividends Payable [Line Items]
Common stock dividends declared (in dollars per share)	$ 0.01

New Accounting Standards - Narr

New Accounting Standards - Narrative (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2020USD ($)pool		Sep. 30, 2020USD ($)		Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of portfolio pools | pool	8
Allowance for credit losses	$ 308,794	[1]	$ 149,887	[1]	$ 72,781	$ 70,774
Cumulative effect adjustment	1,068,501		1,162,933		1,920,669	1,900,249
Net deferred tax assets	91,704		47,709
Increase in common equity tier one capital	129,500
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment	$ (148,769)		(57,169)		$ 683,682	657,475
Cumulative effect adjustment related to ASU adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			177,289
Cumulative effect adjustment			(132,919)	[2]		(182)	[3]
Noncredit discount related to noncredit factors			6,700
Cumulative effect adjustment related to ASU adoption | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			177,300
Cumulative effect adjustment related to ASU adoption | Accounting Standards Update 2016-13, Transfer Of Discounts On Previously Acquired Loans
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			1,500
Cumulative effect adjustment related to ASU adoption | Accounting Standards Update 2016-13, Changes From Incurred Loss Model To CECL Model
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			175,800
Cumulative effect adjustment related to ASU adoption | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment			(132,919)	[2]		$ (182)	[3]
Net deferred tax assets			$ 42,900
[1]	Prior to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020, this line represented the allowance for loan and lease losses under the incurred loss model.
[2]	Cumulative effect adjustment related to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020. For additional information, see Note 2, " New Accounting Pronouncements ".
[3]	Cumulative effect adjustment related to the Company's adoption of ASU 2016-02 and subsequent related ASUs on October 1, 2019.

New Accounting Standards - Comp

New Accounting Standards - Composition of Loans and Allowance by Portfolio Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020		Sep. 30, 2020		Dec. 31, 2019	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			$ 10,076,142
Less: Unamortized discount on acquired loans			0
Unearned net deferred fees and costs and net loans in process			0
Financing receivable, before allowance for credit loss	$ 9,517,876		10,076,142
Allowance for credit losses	(308,794)	[1]	(149,887)	[1]	$ (72,781)	$ (70,774)
Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Financing receivable, before allowance for credit loss	5,030,861		5,355,401
Allowance for credit losses	(174,324)		(85,233)		(17,462)	(16,827)
Agriculture
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,722,696
Financing receivable, before allowance for credit loss	1,635,952		1,722,696
Allowance for credit losses	(46,979)		(27,018)		(32,029)	(30,819)
Commercial non-real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			2,165,038
Financing receivable, before allowance for credit loss	2,054,478		2,165,038
Allowance for credit losses	(75,955)		(27,599)		(17,389)	(17,567)
Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			730,812
Financing receivable, before allowance for credit loss	708,086		730,812
Allowance for credit losses	(9,672)		(7,465)		(4,620)	(4,095)
Consumer and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			102,195
Financing receivable, before allowance for credit loss	88,499		102,195
Allowance for credit losses	(1,864)		(2,572)		$ (1,281)	$ (1,466)
Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Construction and development | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			509,644
Financing receivable, before allowance for credit loss	482,462		509,644
Allowance for credit losses	(18,714)		(7,012)
Owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,417,394
Financing receivable, before allowance for credit loss	1,411,558		1,417,394
Allowance for credit losses	(25,086)		(20,530)
Non-owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			2,894,380
Financing receivable, before allowance for credit loss	2,660,682		2,894,380
Allowance for credit losses	(120,751)		(50,965)
Multifamily residential real estate | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			533,983
Financing receivable, before allowance for credit loss	476,159		533,983
Allowance for credit losses	$ (9,773)		(6,726)
Adoption of ASU 2016-13 as amended
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,498
Less: Unamortized discount on acquired loans			0
Unearned net deferred fees and costs and net loans in process			0
Financing receivable, before allowance for credit loss			1,498
Allowance for credit losses			(177,289)
Adoption of ASU 2016-13 as amended | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Allowance for credit losses			(117,928)
Adoption of ASU 2016-13 as amended | Agriculture
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			55
Allowance for credit losses			(24,360)
Adoption of ASU 2016-13 as amended | Commercial non-real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(85)
Allowance for credit losses			(32,938)
Adoption of ASU 2016-13 as amended | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			23
Allowance for credit losses			(2,595)
Adoption of ASU 2016-13 as amended | Consumer and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(20)
Allowance for credit losses			532
Adoption of ASU 2016-13 as amended | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Adoption of ASU 2016-13 as amended | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Adoption of ASU 2016-13 as amended | Construction and development | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Allowance for credit losses			(11,963)
Adoption of ASU 2016-13 as amended | Owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			36
Allowance for credit losses			(4,298)
Adoption of ASU 2016-13 as amended | Non-owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,497
Allowance for credit losses			(98,986)
Adoption of ASU 2016-13 as amended | Multifamily residential real estate | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(8)
Allowance for credit losses			(2,681)
Adjusted Balance October 1, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			10,077,640
Less: Unamortized discount on acquired loans			0
Unearned net deferred fees and costs and net loans in process			0
Financing receivable, before allowance for credit loss			10,077,640
Allowance for credit losses			(327,176)
Adjusted Balance October 1, 2020 | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Allowance for credit losses			(203,161)
Adjusted Balance October 1, 2020 | Agriculture
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,722,751
Allowance for credit losses			(51,378)
Adjusted Balance October 1, 2020 | Commercial non-real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			2,164,953
Allowance for credit losses			(60,537)
Adjusted Balance October 1, 2020 | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			730,835
Allowance for credit losses			(10,060)
Adjusted Balance October 1, 2020 | Consumer and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			102,175
Allowance for credit losses			(2,040)
Adjusted Balance October 1, 2020 | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Adjusted Balance October 1, 2020 | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Adjusted Balance October 1, 2020 | Construction and development | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			509,644
Allowance for credit losses			(18,975)
Adjusted Balance October 1, 2020 | Owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,417,430
Allowance for credit losses			(24,828)
Adjusted Balance October 1, 2020 | Non-owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			2,895,877
Allowance for credit losses			(149,951)
Adjusted Balance October 1, 2020 | Multifamily residential real estate | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			533,975
Allowance for credit losses			(9,407)
Reported Balance at September 30, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			10,111,602
Less: Unamortized discount on acquired loans			(8,215)
Unearned net deferred fees and costs and net loans in process			(27,245)
Financing receivable, before allowance for credit loss			10,076,142
Allowance for credit losses			(149,887)
Reported Balance at September 30, 2020 | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			5,274,941
Allowance for credit losses			(84,496)
Reported Balance at September 30, 2020 | Agriculture
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,724,350
Allowance for credit losses			(27,018)
Reported Balance at September 30, 2020 | Commercial non-real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			2,181,656
Allowance for credit losses			(27,599)
Reported Balance at September 30, 2020 | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			830,102
Allowance for credit losses			(8,202)
Reported Balance at September 30, 2020 | Consumer and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Allowance for credit losses			(2,572)
Reported Balance at September 30, 2020 | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			63,206
Reported Balance at September 30, 2020 | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			37,347
Reclassification
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Less: Unamortized discount on acquired loans			0
Unearned net deferred fees and costs and net loans in process			0
Allowance for credit losses			0
Reclassification | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(5,274,941)
Allowance for credit losses			(84,496)
Reclassification | Agriculture
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Allowance for credit losses			0
Reclassification | Commercial non-real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Allowance for credit losses			0
Reclassification | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(97,099)
Allowance for credit losses			(737)
Reclassification | Consumer and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			100,553
Allowance for credit losses			0
Reclassification | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(63,206)
Reclassification | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(37,347)
Reclassification | Construction and development | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			512,539
Allowance for credit losses			7,012
Reclassification | Owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,420,061
Allowance for credit losses			20,530
Reclassification | Non-owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			2,902,612
Allowance for credit losses			50,965
Reclassification | Multifamily residential real estate | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			536,828
Allowance for credit losses			6,726
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(35,460)
Less: Unamortized discount on acquired loans			8,215
Unearned net deferred fees and costs and net loans in process			27,245
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Agriculture
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(1,654)
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Commercial non-real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(16,618)
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Residential real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(2,191)
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Consumer and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			1,642
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Consumer
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Construction and development | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(2,895)
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(2,667)
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Non-owner-occupied CRE | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(8,232)
Allowance for credit losses			0
Unamortized Discounts, Unearned Net Deferred Fees and Net Loans and Process Included in Amortized Cost | Multifamily residential real estate | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total financing receivables, gross			(2,845)
Allowance for credit losses			$ 0
[1]	Prior to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020, this line represented the allowance for loan and lease losses under the incurred loss model.

Securities Available for Sale -

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 2,016,551	$ 1,726,962
Gross Unrealized Gains	43,901	47,790
Gross Unrealized Losses	(837)	(126)
Estimated Fair Value	2,059,615	1,774,626
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	24,991	49,924
Gross Unrealized Gains	23	228
Gross Unrealized Losses	0	0
Estimated Fair Value	25,014	50,152
U.S. Agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	24,975	24,974
Gross Unrealized Gains	0	86
Gross Unrealized Losses	(272)	0
Estimated Fair Value	24,703	25,060
Mortgage-backed securities | Government National Mortgage Association
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	424,756	485,689
Gross Unrealized Gains	10,220	11,481
Gross Unrealized Losses	(102)	(43)
Estimated Fair Value	434,874	497,127
Mortgage-backed securities | Federal Home Loan Mortgage Corporation
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	769,254	578,650
Gross Unrealized Gains	17,187	18,919
Gross Unrealized Losses	(65)	(9)
Estimated Fair Value	786,376	597,560
Mortgage-backed securities | Federal National Mortgage Association
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	455,651	287,842
Gross Unrealized Gains	7,301	7,788
Gross Unrealized Losses	(206)	(16)
Estimated Fair Value	462,746	295,614
Mortgage-backed securities | Small Business Assistance Program
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	264,798	244,653
Gross Unrealized Gains	7,829	7,884
Gross Unrealized Losses	(192)	(58)
Estimated Fair Value	272,435	252,479
States and political subdivision securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	51,120	54,224
Gross Unrealized Gains	1,297	1,356
Gross Unrealized Losses	0	0
Estimated Fair Value	52,417	55,580
Other
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,006	1,006
Gross Unrealized Gains	44	48
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 1,050	$ 1,054

Securities Available for Sale_2

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Investments by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Amortized  Cost
Due in one year or less	$ 42,973	$ 67,131
Due after one year through five years	48,047	51,779
Due after five years through ten years	10,066	10,212
Due after ten years	0	0
Amortized  Cost	101,086	129,122
Estimated Fair Value
Due in one year or less	43,103	67,456
Due after one year through five years	48,499	52,694
Due after five years through ten years	10,532	10,642
Due after ten years	0	0
Estimated Fair Value	102,134	130,792
Amortized  Cost	2,016,551	1,726,962
Estimated Fair Value	2,059,615	1,774,626
Securities without contractual maturities, Amortized Cost	1,006	1,006
Securities without contractual maturities, Fair Value	1,050	1,054
Mortgage-backed securities
Estimated Fair Value
Amortized  Cost	1,914,459	1,596,834
Estimated Fair Value	$ 1,956,431	$ 1,642,780

Securities Available for Sale_3

Securities Available for Sale - Narrative (Details)	3 Months Ended
	Dec. 31, 2020USD ($)security	Dec. 31, 2019USD ($)	Sep. 30, 2020USD ($)security
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of securities available for sale	$ 0	$ 0
Gross gains realized	0	0
Gross loss realized	0	0
Securities pledged as collateral	$ 1,070,000,000		$ 1,100,000,000
Percentage of investment portfolio in continuous loss position (as a percent)	9.00%		6.00%
Debt securities, allowance for credit losses	$ 0
Other than temporary impairment losses recognized in earnings		$ 0
Number of securities in an unrealized loss position (securities) | security	22		18

Securities Available for Sale_4

Securities Available for Sale - Schedule of Gross Unrealized Losses on Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	$ 171,502	$ 71,547
12 months or more, Estimated Fair Value	8,388	27,897
Estimated Fair Value	179,890	99,444
12 months or more, Unrealized Losses	(825)	(103)
Less than 12 months, Unrealized Losses	(12)	(23)
Unrealized Losses	(837)	(126)
U.S. Agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	24,703	0
12 months or more, Estimated Fair Value	0	0
Estimated Fair Value	24,703	0
12 months or more, Unrealized Losses	(272)	0
Less than 12 months, Unrealized Losses	0	0
Unrealized Losses	(272)	0
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Estimated Fair Value	146,799	71,547
12 months or more, Estimated Fair Value	8,388	27,897
Estimated Fair Value	155,187	99,444
12 months or more, Unrealized Losses	(553)	(103)
Less than 12 months, Unrealized Losses	(12)	(23)
Unrealized Losses	$ (565)	$ (126)

Loans and Allowance for Credi_3

Loans and Allowance for Credit Losses - Composition of Loans at Amortized Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	$ 9,517,876	$ 10,076,142
Less: Fair Value Option Loans	611,588	655,185
Less: Guaranteed Loans ¹	829,859	862,884
Total	8,076,429	8,558,073
Total commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	5,030,861	5,355,401
Less: Fair Value Option Loans	371,502	396,210
Less: Guaranteed Loans ¹	74,976	75,870
Total	4,584,383	4,883,321
Total commercial real estate | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	482,462	509,644
Less: Fair Value Option Loans	0	0
Less: Guaranteed Loans ¹	0	0
Total	482,462	509,644
Total commercial real estate | Owner-occupied CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	1,411,558	1,417,394
Less: Fair Value Option Loans	107,541	109,097
Less: Guaranteed Loans ¹	47,808	48,468
Total	1,256,209	1,259,829
Total commercial real estate | Non-owner-occupied CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	2,660,682	2,894,380
Less: Fair Value Option Loans	260,916	283,266
Less: Guaranteed Loans ¹	27,168	27,402
Total	2,372,598	2,583,712
Total commercial real estate | Multifamily residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	476,159	533,983
Less: Fair Value Option Loans	3,045	3,847
Less: Guaranteed Loans ¹	0	0
Total	473,114	530,136
Agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	1,635,952	1,722,696
Less: Fair Value Option Loans	115,925	129,041
Less: Guaranteed Loans ¹	39,426	42,353
Total	1,480,601	1,551,302
Commercial non-real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	2,054,478	2,165,038
Less: Fair Value Option Loans	124,161	129,934
Less: Guaranteed Loans ¹	715,163	744,371
Total	1,215,154	1,290,733
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	708,086	730,812
Less: Fair Value Option Loans	0	0
Less: Guaranteed Loans ¹	294	290
Total	707,792	730,522
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, before allowance for credit loss	88,499	102,195
Less: Fair Value Option Loans	0
Less: Guaranteed Loans ¹	0	0
Total	$ 88,499	$ 102,195

Loans and Allowance for Credi_4

Loans and Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Thousands	Oct. 01, 2020	Dec. 31, 2020		Dec. 31, 2019	Mar. 31, 2020	Sep. 30, 2020		Sep. 30, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan held for sale		$ 11,638				$ 12,371
Financing receivable, fair value option		611,588				655,185
Loans at fair value under the fair value option		611,588				655,185
Loans greater than 90 days past due and still accruing interest						0
Specific reserves included in the allowance for loan losses for TDRs		8,500			$ 11,000
Troubled debt restructuring, commitments to lend additional funds		0				0
Transfers out of troubled debt restructuring status		0		$ 0
Allowance for credit losses		308,794	[1]	72,781		149,887	[1]	$ 70,774
Reserve for unfunded loan commitments		2,300				2,400
(Reversal of) provision for unfunded commitments		(100)		200
(Reversal of) provision for credit losses on loans		$ 11,976		$ 8,050
Cumulative effect adjustment related to ASU adoption
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit losses						$ 177,289
(Reversal of) provision for credit losses on loans	$ 177,300
[1]	Prior to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020, this line represented the allowance for loan and lease losses under the incurred loss model.

Loans and Allowance for Credi_5

Loans and Allowance for Credit Losses - Schedule of Past Due and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Financing Receivable, Past Due [Line Items]
Nonaccrual	$ 277,772	$ 322,146
Financing receivable, before allowance for credit loss and fair value option	8,906,288	9,448,197
Financing receivables, not past due	8,906,239	9,448,197
Total commercial real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	67,798	73,146
Financing receivable, before allowance for credit loss and fair value option	4,659,359	4,873,003
Financing receivables, not past due	4,659,359	4,873,003
Total commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Nonaccrual	14,257
Financing receivable, before allowance for credit loss and fair value option	482,462
Financing receivables, not past due	482,462
Total commercial real estate | Owner-occupied CRE
Financing Receivable, Past Due [Line Items]
Nonaccrual	16,776
Financing receivable, before allowance for credit loss and fair value option	1,304,017
Financing receivables, not past due	1,304,017
Total commercial real estate | Non-owner-occupied CRE
Financing Receivable, Past Due [Line Items]
Nonaccrual	36,765
Financing receivable, before allowance for credit loss and fair value option	2,399,766
Financing receivables, not past due	2,399,766
Total commercial real estate | Multifamily residential real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	0
Financing receivable, before allowance for credit loss and fair value option	473,114
Financing receivables, not past due	473,114
Agriculture
Financing Receivable, Past Due [Line Items]
Nonaccrual	185,633	217,642
Financing receivable, before allowance for credit loss and fair value option	1,520,027	1,595,039
Financing receivables, not past due	1,520,027	1,595,039
Commercial non-real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	17,497	26,843
Financing receivable, before allowance for credit loss and fair value option	1,930,317	2,051,663
Financing receivables, not past due	1,930,317	2,051,663
Residential real estate
Financing Receivable, Past Due [Line Items]
Nonaccrual	6,774	4,441
Financing receivable, before allowance for credit loss and fair value option	708,086	828,054
Financing receivables, not past due	708,086	828,054
Consumer and other
Financing Receivable, Past Due [Line Items]
Nonaccrual	70	74
Financing receivable, before allowance for credit loss and fair value option	88,499	100,438
Financing receivables, not past due	88,450	100,438
Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	8,592,493
Current or Less Than 30 Days Past Due | Total commercial real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	4,574,434
Current or Less Than 30 Days Past Due | Total commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	468,025
Current or Less Than 30 Days Past Due | Total commercial real estate | Owner-occupied CRE
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	1,286,830
Current or Less Than 30 Days Past Due | Total commercial real estate | Non-owner-occupied CRE
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	2,346,904
Current or Less Than 30 Days Past Due | Total commercial real estate | Multifamily residential real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	472,675
Current or Less Than 30 Days Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	1,322,075
Current or Less Than 30 Days Past Due | Commercial non-real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	1,909,610
Current or Less Than 30 Days Past Due | Residential real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	698,146
Current or Less Than 30 Days Past Due | Consumer and other
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	88,228
30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	35,974
30-89 Days Past Due | Total commercial real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	17,127
30-89 Days Past Due | Total commercial real estate | Construction and development
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	180
30-89 Days Past Due | Total commercial real estate | Owner-occupied CRE
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	411
30-89 Days Past Due | Total commercial real estate | Non-owner-occupied CRE
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	16,097
30-89 Days Past Due | Total commercial real estate | Multifamily residential real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	439
30-89 Days Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	12,319
30-89 Days Past Due | Commercial non-real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	3,210
30-89 Days Past Due | Residential real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	3,166
30-89 Days Past Due | Consumer and other
Financing Receivable, Past Due [Line Items]
Financing receivables, past due	$ 152
Current or Less Than 30 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		9,051,121
Current or Less Than 30 Days Past Due | Total commercial real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		4,790,963
Current or Less Than 30 Days Past Due | Agriculture
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		1,317,377
Current or Less Than 30 Days Past Due | Commercial non-real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		2,021,308
Current or Less Than 30 Days Past Due | Residential real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		821,154
Current or Less Than 30 Days Past Due | Consumer and other
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		100,319
90 Days Past Due and Still Accruing
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		74,930
90 Days Past Due and Still Accruing | Total commercial real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		8,894
90 Days Past Due and Still Accruing | Agriculture
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		60,020
90 Days Past Due and Still Accruing | Commercial non-real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		3,512
90 Days Past Due and Still Accruing | Residential real estate
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		2,459
90 Days Past Due and Still Accruing | Consumer and other
Financing Receivable, Past Due [Line Items]
Financing receivables, past due		$ 45

Loans and Allowance for Credi_6

Loans and Allowance for Credit Losses - Schedule of the Company's Nonaccrual Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	$ 277,772	$ 322,146
Nonaccrual Loans with No Related ACL	181,941
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	2,250
Total commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	67,798	73,146
Nonaccrual Loans with No Related ACL	19,722
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	1,840
Total commercial real estate | Construction and development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	14,257
Nonaccrual Loans with No Related ACL	0
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	110
Total commercial real estate | Owner-occupied CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	16,776
Nonaccrual Loans with No Related ACL	8,036
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	13
Total commercial real estate | Non-owner-occupied CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	36,765
Nonaccrual Loans with No Related ACL	11,686
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	1,717
Total commercial real estate | Multifamily residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	0
Nonaccrual Loans with No Related ACL	0
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	0
Agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	185,633	217,642
Nonaccrual Loans with No Related ACL	154,508
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	382
Commercial non-real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	17,497	26,843
Nonaccrual Loans with No Related ACL	7,711
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	2
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	6,774	4,441
Nonaccrual Loans with No Related ACL	0
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	25
Consumer and other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	70	$ 74
Nonaccrual Loans with No Related ACL	0
Interest Income Recognized on Nonaccrual Loans	0
Accrued Interest Written Off on Nonaccrual Loans	$ 1

Loans and Allowance for Credi_7

Loans and Allowance for Credit Losses - Schedule of the Composition of the Loan Portfolio by Internal Risk Rating (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 690,785
2020	2,533,428
2019	1,308,052
2018	1,035,175
2017	838,782
Prior to 2017	870,237
Revolving Loans	1,629,480
Revolving Loans Converted to Term Loans	349
Financing receivable, before allowance for credit loss and fair value option	8,906,288	$ 9,448,197
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	588,201
2020	2,343,342
2019	1,202,111
2018	772,530
2017	734,064
Prior to 2017	804,422
Revolving Loans	1,343,997
Revolving Loans Converted to Term Loans	349
Financing receivable, before allowance for credit loss and fair value option	7,789,016	7,789,080
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	51,244
2020	54,920
2019	50,876
2018	119,918
2017	50,672
Prior to 2017	31,398
Revolving Loans	90,597
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	449,625	945,195
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	49,745
2020	134,727
2019	51,042
2018	120,412
2017	52,600
Prior to 2017	30,146
Revolving Loans	186,252
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	624,924	685,959
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,595
2020	439
2019	4,023
2018	22,315
2017	1,446
Prior to 2017	4,271
Revolving Loans	8,634
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	42,723	27,963
Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit loss and fair value option		0
Total commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	477,305
2020	1,137,244
2019	861,503
2018	745,749
2017	602,392
Prior to 2017	616,625
Revolving Loans	218,482
Revolving Loans Converted to Term Loans	59
Financing receivable, before allowance for credit loss and fair value option	4,659,359	4,873,003
Total commercial real estate | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2021	101,347
2020	160,917
2019	108,280
2018	43,576
2017	2,570
Prior to 2017	824
Revolving Loans	64,948
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	482,462
Total commercial real estate | Owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	109,145
2020	379,382
2019	237,197
2018	142,195
2017	184,465
Prior to 2017	199,845
Revolving Loans	51,729
Revolving Loans Converted to Term Loans	59
Financing receivable, before allowance for credit loss and fair value option	1,304,017
Total commercial real estate | Non-owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	194,514
2020	488,841
2019	411,069
2018	467,751
2017	397,935
Prior to 2017	359,299
Revolving Loans	80,357
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	2,399,766
Total commercial real estate | Multifamily residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	72,299
2020	108,104
2019	104,957
2018	92,227
2017	17,422
Prior to 2017	56,657
Revolving Loans	21,448
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	473,114
Total commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	423,809
2020	1,057,622
2019	797,795
2018	568,415
2017	566,226
Prior to 2017	577,073
Revolving Loans	160,127
Revolving Loans Converted to Term Loans	59
Financing receivable, before allowance for credit loss and fair value option	4,151,126	4,062,814
Total commercial real estate | Pass | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2021	86,339
2020	160,884
2019	108,053
2018	30,830
2017	2,570
Prior to 2017	824
Revolving Loans	63,584
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	453,084
Total commercial real estate | Pass | Owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	104,322
2020	372,920
2019	227,194
2018	117,287
2017	164,280
Prior to 2017	185,366
Revolving Loans	51,397
Revolving Loans Converted to Term Loans	59
Financing receivable, before allowance for credit loss and fair value option	1,222,825
Total commercial real estate | Pass | Non-owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	161,105
2020	423,025
2019	360,220
2018	348,757
2017	382,487
Prior to 2017	334,667
Revolving Loans	44,898
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	2,055,159
Total commercial real estate | Pass | Multifamily residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	72,043
2020	100,793
2019	102,328
2018	71,541
2017	16,889
Prior to 2017	56,216
Revolving Loans	248
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	420,058
Total commercial real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	23,398
2020	3,408
2019	40,321
2018	104,501
2017	23,975
Prior to 2017	25,013
Revolving Loans	21,532
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	242,148	577,399
Total commercial real estate | Special Mention | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2021	3,686
2020	0
2019	200
2018	0
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	3,886
Total commercial real estate | Special Mention | Owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	465
2020	1,853
2019	2,170
2018	6,651
2017	8,481
Prior to 2017	8,032
Revolving Loans	332
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	27,984
Total commercial real estate | Special Mention | Non-owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	18,991
2020	1,555
2019	35,322
2018	77,164
2017	15,448
Prior to 2017	16,874
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	165,354
Total commercial real estate | Special Mention | Multifamily residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	256
2020	0
2019	2,629
2018	20,686
2017	46
Prior to 2017	107
Revolving Loans	21,200
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	44,924
Total commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	30,098
2020	76,214
2019	20,170
2018	72,833
2017	12,191
Prior to 2017	14,539
Revolving Loans	36,823
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	262,868	229,467
Total commercial real estate | Substandard | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2021	11,322
2020	33
2019	0
2018	12,746
2017	0
Prior to 2017	0
Revolving Loans	1,364
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	25,465
Total commercial real estate | Substandard | Owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	4,358
2020	4,609
2019	4,643
2018	18,257
2017	11,704
Prior to 2017	6,447
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	50,018
Total commercial real estate | Substandard | Non-owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	14,418
2020	64,261
2019	15,527
2018	41,830
2017	0
Prior to 2017	7,758
Revolving Loans	35,459
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	179,253
Total commercial real estate | Substandard | Multifamily residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	7,311
2019	0
2018	0
2017	487
Prior to 2017	334
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	8,132
Total commercial real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	3,217
2018	0
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	3,217	3,323
Total commercial real estate | Doubtful | Construction and development
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	27
2018	0
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	27
Total commercial real estate | Doubtful | Owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	3,190
2018	0
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	3,190
Total commercial real estate | Doubtful | Non-owner-occupied CRE
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	0
Total commercial real estate | Doubtful | Multifamily residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	0
Total commercial real estate | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit loss and fair value option		0
Agriculture
Financing Receivable, Credit Quality Indicator [Line Items]
2021	90,207
2020	288,086
2019	128,781
2018	162,532
2017	147,712
Prior to 2017	74,885
Revolving Loans	627,824
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	1,520,027	1,595,039
Agriculture | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	56,160
2020	222,029
2019	105,591
2018	85,249
2017	82,726
Prior to 2017	62,253
Revolving Loans	460,060
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	1,074,068	968,875
Agriculture | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	21,040
2020	29,166
2019	7,402
2018	13,400
2017	23,817
Prior to 2017	4,511
Revolving Loans	49,451
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	148,787	265,714
Agriculture | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	11,412
2020	36,842
2019	15,034
2018	41,653
2017	39,723
Prior to 2017	8,121
Revolving Loans	114,838
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	267,623	348,910
Agriculture | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,595
2020	49
2019	754
2018	22,230
2017	1,446
Prior to 2017	0
Revolving Loans	3,475
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	29,549	11,540
Agriculture | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit loss and fair value option		0
Commercial non-real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	42,534
2020	869,488
2019	211,522
2018	69,885
2017	55,492
Prior to 2017	50,484
Revolving Loans	630,904
Revolving Loans Converted to Term Loans	8
Financing receivable, before allowance for credit loss and fair value option	1,930,317	2,051,663
Commercial non-real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	28,084
2020	827,457
2019	195,666
2018	63,526
2017	52,661
Prior to 2017	43,956
Revolving Loans	573,735
Revolving Loans Converted to Term Loans	8
Financing receivable, before allowance for credit loss and fair value option	1,785,093	1,851,323
Commercial non-real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	6,500
2020	21,521
2019	2,812
2018	1,714
2017	2,576
Prior to 2017	864
Revolving Loans	19,391
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	55,378	94,401
Commercial non-real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7,950
2020	20,120
2019	12,992
2018	4,561
2017	255
Prior to 2017	1,395
Revolving Loans	32,619
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	79,892	94,316
Commercial non-real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	390
2019	52
2018	84
2017	0
Prior to 2017	4,269
Revolving Loans	5,159
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	9,954	11,623
Commercial non-real estate | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit loss and fair value option		0
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2021	49,273
2020	216,068
2019	89,372
2018	54,108
2017	31,956
Prior to 2017	126,853
Revolving Loans	140,174
Revolving Loans Converted to Term Loans	282
Financing receivable, before allowance for credit loss and fair value option	708,086	828,054
Residential real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	48,697
2020	213,698
2019	86,203
2018	52,442
2017	31,231
Prior to 2017	119,770
Revolving Loans	138,017
Revolving Loans Converted to Term Loans	282
Financing receivable, before allowance for credit loss and fair value option	690,340	806,436
Residential real estate | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	297
2020	825
2019	341
2018	303
2017	304
Prior to 2017	998
Revolving Loans	220
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	3,288	6,972
Residential real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	279
2020	1,545
2019	2,828
2018	1,363
2017	421
Prior to 2017	6,083
Revolving Loans	1,937
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	14,456	13,173
Residential real estate | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior to 2017	2
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	2	1,473
Residential real estate | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit loss and fair value option		0
Consumer and other
Financing Receivable, Credit Quality Indicator [Line Items]
2021	31,466
2020	22,542
2019	16,874
2018	2,901
2017	1,230
Prior to 2017	1,390
Revolving Loans	12,096
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	88,499	100,438
Consumer and other | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	31,451
2020	22,536
2019	16,856
2018	2,898
2017	1,220
Prior to 2017	1,370
Revolving Loans	12,058
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	88,389	99,632
Consumer and other | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	9
2020	0
2019	0
2018	0
2017	0
Prior to 2017	12
Revolving Loans	3
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	24	709
Consumer and other | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	6
2020	6
2019	18
2018	2
2017	10
Prior to 2017	8
Revolving Loans	35
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	85	93
Consumer and other | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	1
2017	0
Prior to 2017	0
Revolving Loans	0
Revolving Loans Converted to Term Loans	0
Financing receivable, before allowance for credit loss and fair value option	$ 1	4
Consumer and other | Loss
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, before allowance for credit loss and fair value option		$ 0

Loans and Allowance for Credi_8

Loans and Allowance for Credit Losses - Schedule of Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Sep. 30, 2020
With an allowance for credit losses recorded:
Recorded Investment		$ 209,762
Unpaid Principal Balance		223,173
Related Allowance for Credit Losses		42,993
With no allowance for credit losses recorded:
Recorded Investment		503,199
Unpaid Principal Balance		577,774
Total Recorded Investment, Impaired Loans		712,961
Total Unpaid Principal Balance, Impaired Loans		800,947
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	$ 515,400
Interest Income Recognized While on Impaired Status	14,033
Total commercial real estate
With an allowance for credit losses recorded:
Recorded Investment		111,121
Unpaid Principal Balance		114,034
Related Allowance for Credit Losses		25,087
With no allowance for credit losses recorded:
Recorded Investment		121,380
Unpaid Principal Balance		161,211
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	73,422
Interest Income Recognized While on Impaired Status	2,379
Agriculture
With an allowance for credit losses recorded:
Recorded Investment		53,052
Unpaid Principal Balance		55,145
Related Allowance for Credit Losses		8,151
With no allowance for credit losses recorded:
Recorded Investment		308,734
Unpaid Principal Balance		332,272
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	360,397
Interest Income Recognized While on Impaired Status	8,517
Commercial non-real estate
With an allowance for credit losses recorded:
Recorded Investment		39,821
Unpaid Principal Balance		47,571
Related Allowance for Credit Losses		7,822
With no allowance for credit losses recorded:
Recorded Investment		66,542
Unpaid Principal Balance		75,365
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	72,389
Interest Income Recognized While on Impaired Status	2,870
Residential real estate
With an allowance for credit losses recorded:
Recorded Investment		5,670
Unpaid Principal Balance		6,314
Related Allowance for Credit Losses		1,903
With no allowance for credit losses recorded:
Recorded Investment		6,543
Unpaid Principal Balance		8,818
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	9,013
Interest Income Recognized While on Impaired Status	266
Consumer and other
With an allowance for credit losses recorded:
Recorded Investment		98
Unpaid Principal Balance		109
Related Allowance for Credit Losses		30
With no allowance for credit losses recorded:
Recorded Investment		0
Unpaid Principal Balance		$ 108
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	179
Interest Income Recognized While on Impaired Status	$ 1

Loans and Allowance for Credi_9

Loans and Allowance for Credit Losses - Schedule of Acquired Loans (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2019USD ($)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 26,047
Accretion	(1,940)
Reclassification (to) from nonaccretable difference	(2,977)
Balance at end of period	$ 21,130

Loans and Allowance for Cred_10

Loans and Allowance for Credit Losses - Summary of Troubled Debt Restructurings on Accruing and Nonaccrual Financing Receivables (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2020USD ($)contract	Dec. 31, 2019USD ($)contract	Sep. 30, 2020USD ($)
Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 31,088		$ 35,205
Financing receivable, modifications, number of contracts | contract	2	2
Financing receivable, modifications, pre-modification recorded investment	$ 11,340	$ 1,144
Financing receivable, modifications, post-modification recorded investment	$ 11,340	$ 1,444
Change in recorded investment due to principal paydown at time of modification, number of contracts | contract	0	0
Change in recorded investment due to principal paydown at time of modification, pre-modification recorded investment	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, post-modification recorded investment	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, number of contracts | contract	0	0
Change in recorded investment due to chargeoffs at time of modification, pre-modification recorded investment	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, post-modification recorded investment	0	$ 0
Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 52,592		62,792
Financing receivable, modifications, number of contracts | contract	4	13
Financing receivable, modifications, pre-modification recorded investment	$ 3,524	$ 4,501
Financing receivable, modifications, post-modification recorded investment	$ 3,524	$ 4,501
Change in recorded investment due to principal paydown at time of modification, number of contracts | contract	0	0
Change in recorded investment due to principal paydown at time of modification, pre-modification recorded investment	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, post-modification recorded investment	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, number of contracts | contract	0	0
Change in recorded investment due to chargeoffs at time of modification, pre-modification recorded investment	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, post-modification recorded investment	0	$ 0
Total commercial real estate | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 19,157		23,215
Financing receivable, modifications, number of contracts | contract	1	0
Financing receivable, modifications, pre-modification recorded investment	$ 10,640	$ 0
Financing receivable, modifications, post-modification recorded investment	10,640	$ 0
Total commercial real estate | Accruing | Construction and development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 1,364
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Total commercial real estate | Accruing | Owner-occupied CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 5,590
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Total commercial real estate | Accruing | Non-owner-occupied CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 12,203
Financing receivable, modifications, number of contracts | contract	1
Financing receivable, modifications, pre-modification recorded investment	$ 10,640
Financing receivable, modifications, post-modification recorded investment	10,640
Total commercial real estate | Accruing | Multifamily residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 0
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Total commercial real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 11,664		11,913
Financing receivable, modifications, number of contracts | contract	0	1
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 2,216
Financing receivable, modifications, post-modification recorded investment	0	$ 2,216
Total commercial real estate | Nonaccrual | Construction and development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 27
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Total commercial real estate | Nonaccrual | Owner-occupied CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 0
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Total commercial real estate | Nonaccrual | Non-owner-occupied CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 11,637
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Total commercial real estate | Nonaccrual | Multifamily residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 0
Financing receivable, modifications, number of contracts | contract	0
Financing receivable, modifications, pre-modification recorded investment	$ 0
Financing receivable, modifications, post-modification recorded investment	0
Agriculture | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 3,356		2,976
Financing receivable, modifications, number of contracts | contract	1	0
Financing receivable, modifications, pre-modification recorded investment	$ 700	$ 0
Financing receivable, modifications, post-modification recorded investment	700	$ 0
Agriculture | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 35,736		45,971
Financing receivable, modifications, number of contracts | contract	3	10
Financing receivable, modifications, pre-modification recorded investment	$ 2,776	$ 1,455
Financing receivable, modifications, post-modification recorded investment	2,776	$ 1,455
Commercial non-real estate | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 8,304		8,734
Financing receivable, modifications, number of contracts | contract	0	2
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 1,144
Financing receivable, modifications, post-modification recorded investment	0	$ 1,444
Commercial non-real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 5,096		4,803
Financing receivable, modifications, number of contracts | contract	1	2
Financing receivable, modifications, pre-modification recorded investment	$ 748	$ 830
Financing receivable, modifications, post-modification recorded investment	748	$ 830
Residential real estate | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 269		277
Financing receivable, modifications, number of contracts | contract	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0
Residential real estate | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 69		74
Financing receivable, modifications, number of contracts | contract	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0
Consumer and other | Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 2		3
Financing receivable, modifications, number of contracts | contract	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0
Consumer and other | Nonaccrual
Financing Receivable, Troubled Debt Restructuring [Line Items]
Recorded value of TDR balance	$ 27		$ 31
Financing receivable, modifications, number of contracts | contract	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	$ 0	$ 0

Loans and Allowance for Cred_11

Loans and Allowance for Credit Losses - Subsequent Defaults on Modified Loans (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2020USD ($)contract	Dec. 31, 2019USD ($)contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	3	20
Recorded Investment | $	$ 653	$ 17,181
Total commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0	0
Recorded Investment | $	$ 0	$ 0
Total commercial real estate | Construction and development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0
Recorded Investment | $	$ 0
Total commercial real estate | Owner-occupied CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0
Recorded Investment | $	$ 0
Total commercial real estate | Non-owner-occupied CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0
Recorded Investment | $	$ 0
Total commercial real estate | Multifamily residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0
Recorded Investment | $	$ 0
Agriculture
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0	19
Recorded Investment | $	$ 0	$ 14,347
Commercial non-real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	3	1
Recorded Investment | $	$ 653	$ 2,834
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0	0
Recorded Investment | $	$ 0	$ 0
Consumer and other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | contract	0	0
Recorded Investment | $	$ 0	$ 0

Loans and Allowance for Cred_12

Loans and Allowance for Credit Losses - Summary of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Oct. 01, 2020		Dec. 31, 2020		Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	$ 149,887	[1]	$ 149,887	[1]	$ 70,774
Charge-offs			(32,811)		(6,666)
Recoveries			2,453		570
(Reversal of) provision for credit losses on loans			11,976		8,050
Impairment (improvement) of ASC 310-30 loans					53
Allowance for credit losses, ending balance			308,794	[1]	72,781
Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	177,289		177,289
(Reversal of) provision for credit losses on loans	177,300
Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	327,176		327,176
Total commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	85,233		85,233		16,827
Charge-offs			(28,296)		(37)
Recoveries			329		120
(Reversal of) provision for credit losses on loans			(870)		572
Impairment (improvement) of ASC 310-30 loans					(20)
Allowance for credit losses, ending balance			174,324		17,462
Total commercial real estate | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	117,928		117,928
Total commercial real estate | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	203,161		203,161
Total commercial real estate | Construction and development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	7,012		7,012
Charge-offs			(27)
Recoveries			268
(Reversal of) provision for credit losses on loans			(502)
Allowance for credit losses, ending balance			18,714
Total commercial real estate | Construction and development | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	11,963		11,963
Total commercial real estate | Construction and development | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	18,975		18,975
Total commercial real estate | Owner-occupied CRE
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	20,530		20,530
Charge-offs			0
Recoveries			0
(Reversal of) provision for credit losses on loans			258
Allowance for credit losses, ending balance			25,086
Total commercial real estate | Owner-occupied CRE | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	4,298		4,298
Total commercial real estate | Owner-occupied CRE | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	24,828		24,828
Total commercial real estate | Non-owner-occupied CRE
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	50,965		50,965
Charge-offs			(28,269)
Recoveries			61
(Reversal of) provision for credit losses on loans			(992)
Allowance for credit losses, ending balance			120,751
Total commercial real estate | Non-owner-occupied CRE | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	98,986		98,986
Total commercial real estate | Non-owner-occupied CRE | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	149,951		149,951
Total commercial real estate | Multifamily residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	6,726		6,726
Charge-offs			0
Recoveries			0
(Reversal of) provision for credit losses on loans			366
Allowance for credit losses, ending balance			9,773
Total commercial real estate | Multifamily residential real estate | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	2,681		2,681
Total commercial real estate | Multifamily residential real estate | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	9,407		9,407
Agriculture
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	27,018		27,018		30,819
Charge-offs			(2,144)		(4,606)
Recoveries			1,734		103
(Reversal of) provision for credit losses on loans			(3,989)		5,978
Impairment (improvement) of ASC 310-30 loans					(265)
Allowance for credit losses, ending balance			46,979		32,029
Agriculture | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	24,360		24,360
Agriculture | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	51,378		51,378
Commercial non-real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	27,599		27,599		17,567
Charge-offs			(2,043)		(1,481)
Recoveries			245		112
(Reversal of) provision for credit losses on loans			17,216		1,191
Impairment (improvement) of ASC 310-30 loans					0
Allowance for credit losses, ending balance			75,955		17,389
Commercial non-real estate | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	32,938		32,938
Commercial non-real estate | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	60,537		60,537
Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	7,465		7,465		4,095
Charge-offs			(96)		(169)
Recoveries			32		164
(Reversal of) provision for credit losses on loans			(324)		192
Impairment (improvement) of ASC 310-30 loans					338
Allowance for credit losses, ending balance			9,672		4,620
Residential real estate | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	2,595		2,595
Residential real estate | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	10,060		10,060
Consumer and other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	2,572		2,572		1,466
Charge-offs			(232)		(373)
Recoveries			113		71
(Reversal of) provision for credit losses on loans			(57)		117
Impairment (improvement) of ASC 310-30 loans					0
Allowance for credit losses, ending balance			1,864		$ 1,281
Consumer and other | Cumulative effect adjustment related to ASU adoption
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	(532)		(532)
Consumer and other | Adjusted Balance October 1, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning balance	$ 2,040		$ 2,040
[1]	Prior to the adoption of ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , and subsequent related ASUs, on October 1, 2020, this line represented the allowance for loan and lease losses under the incurred loss model.

Derivative Financial Instrume_3

Derivative Financial Instruments - Schedule of Derivative Positions, Notional Amounts and Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Derivative [Line Items]
Gross Asset Fair Value	$ 74,819	$ 83,631
Gross Liability Fair Value	(56,430)	(64,389)
Not Designated as Hedging Instruments
Derivative [Line Items]
Notional Amount	2,275,469	2,182,738
Gross Asset Fair Value	74,819	83,631
Gross Liability Fair Value	(56,430)	(64,389)
Not Designated as Hedging Instruments | Interest rate swaps - FVO loan portfolio | Financial institution counterparties
Derivative [Line Items]
Notional Amount	562,359	592,241
Gross Asset Fair Value	0	0
Gross Liability Fair Value	(54,568)	(62,587)
Not Designated as Hedging Instruments | Interest rate swaps - Other | Financial institution counterparties
Derivative [Line Items]
Notional Amount	708,872	641,189
Gross Asset Fair Value	0	0
Gross Liability Fair Value	(1,516)	(1,672)
Not Designated as Hedging Instruments | Interest rate swaps - Other | Customer counterparties
Derivative [Line Items]
Notional Amount	708,872	641,189
Gross Asset Fair Value	74,495	83,533
Gross Liability Fair Value	0	0
Not Designated as Hedging Instruments | Interest rate caps | Financial institution counterparties
Derivative [Line Items]
Notional Amount	26,538	20,538
Gross Asset Fair Value	2	2
Gross Liability Fair Value	0	0
Not Designated as Hedging Instruments | Interest rate caps | Customer counterparties
Derivative [Line Items]
Notional Amount	26,538	20,538
Gross Asset Fair Value	0	0
Gross Liability Fair Value	(2)	(2)
Not Designated as Hedging Instruments | Risk participation agreements
Derivative [Line Items]
Notional Amount	82,111	80,681
Gross Asset Fair Value	0	0
Gross Liability Fair Value	(22)	(32)
Not Designated as Hedging Instruments | Mortgage loan commitments
Derivative [Line Items]
Notional Amount	79,738	92,278
Gross Asset Fair Value	322	0
Gross Liability Fair Value	0	(96)
Not Designated as Hedging Instruments | Mortgage loan forward sale contracts
Derivative [Line Items]
Notional Amount	80,441	94,084
Gross Asset Fair Value	0	96
Gross Liability Fair Value	$ (322)	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets, gross amount	$ 74,819	$ 83,631
Derivative assets, fair value offset amount	(4,321)	(5,263)
Derivative assets, cash collateral	17,763	20,012
Derivatives-assets	88,261	98,380
Derivative liabilities, gross amount	(56,430)	(64,389)
Derivative liabilities, fair value offset amount	4,321	5,263
Derivative liabilities, cash collateral	51,785	59,028
Derivative Liabilities	(324)	(98)
Collateral held for initial margin	$ 25,100	$ 22,900

Derivative Financial Instrume_5

Derivative Financial Instruments - Effect on the Consolidated Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative interest expense | Interest rate swaps - FVO loan portfolio
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	$ (3,393)	$ (890)
Change in fair value of FVO loans and related derivatives | Interest rate swaps - FVO loan portfolio
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	8,570	12,809
Other derivative income | Interest rate swaps - FVO loan portfolio
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	898	1,597
Other derivative income | Mortgage loan commitments
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	(418)	28
Other derivative income | Mortgage loan forward sale contracts
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	$ 418	$ (28)

The Fair Value Option for Cer_2

The Fair Value Option for Certain Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Eligible item for the fair value option	$ 31,600		$ 37,300
Loans greater than 90 days past due or in nonaccrual status	14,600		21,700
Unpaid principal balance greater than 90 days past due or in nonaccrual status	14,600		26,200
Net increase (decrease) in fair value of loans at fair value	(1,672)	$ (2,124)
Long-term loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total unpaid principal balance of long-term loans	580,000		$ 617,900
Total change in fair value attributable to changes in specific credit risk	1,500	2,100
Long-term loans | Noninterest income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net increase (decrease) in fair value of loans at fair value	$ (10,200)	$ (14,900)

Core Deposits and Other Intan_3

Core Deposits and Other Intangibles - Intangible Assets Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 11,049	$ 11,049
Accumulated amortization	(5,145)	(4,885)
Total	5,904	6,164
Core Deposit Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	7,339	7,339
Accumulated amortization	(4,499)	(4,316)
Total	2,840	3,023
Customer Relationships Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	3,172	3,172
Accumulated amortization	(305)	(244)
Total	2,867	2,928
Other Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	538	538
Accumulated amortization	(341)	(325)
Total	$ 197	$ 213

Core Deposits and Other Intan_4

Core Deposits and Other Intangibles - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of core deposits and other intangibles	$ 0.3	$ 0.4

Core Deposits and Other Intan_5

Core Deposits and Other Intangibles - Schedule of Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Remaining in 2021	$ 754
2022	929
2023	831
2024	742
2025	683
2026 and thereafter	1,965
Total	$ 5,904	$ 6,164

Leases (Details)

Leases (Details) $ in Millions	3 Months Ended
	Dec. 31, 2020USD ($)lease	Dec. 31, 2019USD ($)	Sep. 30, 2020lease
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets
Lease expense | $	$ 1.7	$ 1.7
Number of operating leases, not yet commenced | lease	0		0
Minimum
Lessee, Lease, Description [Line Items]
Lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease term	15 years

Leases - Summary of ROU Assets

Leases - Summary of ROU Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Leases [Abstract]
Operating lease, right-of-use asset	$ 21,264	$ 22,709
Operating lease, liability	$ 22,586	$ 24,114
Weighted average remaining lease term (in years)	6 years 2 months 15 days	6 years 3 months 14 days
Weighted average discount rate (as a percentage)	1.82%	1.83%
Operating lease liability, statement of financial position [Extensible List]	us-gaap:AccruedLiabilitiesAndOtherLiabilities

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating cash flows paid for operating leases	$ 1,482	$ 1,410
Operating leases	$ 987	$ 624

Leases - Remaining Minimum Leas

Leases - Remaining Minimum Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Leases [Abstract]
Remaining in 2021	$ 4,383
2022	4,701
2023	4,149
2024	3,410
2025	2,469
2026 and thereafter	5,395
Total undiscounted lease payments	24,507
Less: Amounts representing interest	(1,921)
Lease liability	$ 22,586	$ 24,114

Securities Sold Under Agreeme_3

Securities Sold Under Agreements to Repurchase - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Abstract]
Securities sold under agreements to repurchase	$ 93.6	$ 82.6
Securities sold under agreements to repurchase, fair value of collateral	$ 95.8	$ 84.7
Securities sold under agreements to repurchase, collateral, percentage of borrowed funds (as a percent)	102.00%

Securities Sold Under Agreeme_4

Securities Sold Under Agreements to Repurchase - Maturity Schedule of Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	$ 80,355	$ 65,506
Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	80,355	65,506
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	80,355	65,506
Overnight and Continuous | Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	80,355	65,506
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	0	0
Up to 30 Days | Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	0	0
30-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	0	0
30-90 Days | Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	0	0
Greater than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	0	0
Greater than 90 Days | Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	$ 0	$ 0

FHLB Advances and Other Borro_3

FHLB Advances and Other Borrowings - Schedule of Advances, Related Party Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Total	$ 120,000	$ 195,000
Notes payable to banks
Debt Instrument [Line Items]
Federal Home Loan Bank (FHLB) notes payable and fed funds advance	$ 120,000	120,000
Notes payable to banks | Minimum
Debt Instrument [Line Items]
Stated interest rate (as a percent)	2.76%
Notes payable to banks | Maximum
Debt Instrument [Line Items]
Stated interest rate (as a percent)	2.88%
Federal Home Loan Bank fed funds advance
Debt Instrument [Line Items]
Federal Home Loan Bank (FHLB) notes payable and fed funds advance	$ 0	$ 75,000

FHLB Advances and Other Borro_4

FHLB Advances and Other Borrowings - Narrative (Details) - USD ($)	Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Current borrowing capacity	$ 1,990,000,000	$ 2,030,000,000
Loans pledged to the Federal Home Loan Bank	3,930,000,000	4,070,000,000
Revolving Credit Facility | FRB Discount Window Loan
Debt Instrument [Line Items]
Borrowing capacity	943,500,000	947,700,000
Loans pledged to the Federal Reserve Board Discount Window	1,110,000,000	1,170,000,000
Letter of Credit | Federal Home Loan Bank
Debt Instrument [Line Items]
Borrowing capacity	0	75,000,000
Additional Letters of Credit | Federal Home Loan Bank
Debt Instrument [Line Items]
Borrowing capacity	$ 10,200,000	$ 14,600,000

FHLB Advances and Other Borro_5

FHLB Advances and Other Borrowings - Schedule of Due or Callable Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
Total	$ 108,866	$ 108,832
FHLB Advances and Related Party Notes Payable
Debt Instrument [Line Items]
Remaining in 2021	0
2022	30,000
2023	30,000
2024	60,000
2025	0
2026 and thereafter	0
Total	$ 120,000

Subordinated Debentures and S_3

Subordinated Debentures and Subordinated Notes Payable - Junior Subordinated Deferrable Interest Debentures (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2020USD ($)quartertrust$ / sharesshares	Sep. 30, 2020USD ($)
Debt Instrument [Line Items]
Total subordinated debentures and subordinated notes payable	$ 108,866	$ 108,832
Junior Subordinated Debt
Debt Instrument [Line Items]
Total subordinated debentures and subordinated notes payable	73,866	73,832
Common shares held in other assets	$ 2,520	$ 2,520
Trust Preferred Securities Subject to Mandatory Redemption
Debt Instrument [Line Items]
Number of trusts | trust	7
Number of shares caused to be issued (in shares) | shares	73,400
Par value per shares issued (in dollars per share) | $ / shares	$ 1,000
Deferred interest payments, number of consecutive quarters | quarter	20
Trust Preferred Securities Subject to Mandatory Redemption | London Interbank Offered Rate (LIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.48%
Trust Preferred Securities Subject to Mandatory Redemption | London Interbank Offered Rate (LIBOR) | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.35%

Subordinated Debentures and S_4

Subordinated Debentures and Subordinated Notes Payable - Subordinated Notes Payable (Details) - Subordinated Debt - USD ($)	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2015
Debt Instrument [Line Items]
Face amount of debt issued		$ 35,000,000
Stated interest rate (as a percent)		4.875%
Redemption price, percentage of principal (as a percent)	100.00%
London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.15%

Subordinated Debentures and S_5

Subordinated Debentures and Subordinated Notes Payable - Summary of Subordinated Debentures and Notes Payable (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2015
Debt Instrument [Line Items]
Total	$ 108,866	$ 108,832
Junior Subordinated Debt
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	75,920	75,920
Total junior subordinated debentures payable, common shares held in other assets	2,520	2,520
Less: fair value adjustment	(2,054)	(2,088)
Total	73,866	73,832
Junior Subordinated Debt | GW Statutory Trust IV, variable rate of 2.85%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	23,093	23,093
Total junior subordinated debentures payable, common shares held in other assets	$ 693	693
Junior Subordinated Debt | GW Statutory Trust IV, variable rate of 2.85%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.85%
Junior Subordinated Debt | GW Statutory Trust VI, variable rate of 1.48%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 30,928	30,928
Total junior subordinated debentures payable, common shares held in other assets	$ 928	928
Junior Subordinated Debt | GW Statutory Trust VI, variable rate of 1.48%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.48%
Junior Subordinated Debt | SSB Trust II, variable rate of 1.85%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 2,062	2,062
Total junior subordinated debentures payable, common shares held in other assets	$ 62	62
Junior Subordinated Debt | SSB Trust II, variable rate of 1.85%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.85%
Junior Subordinated Debt | HF Capital Trust III, variable rate of 3.35%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 5,155	5,155
Total junior subordinated debentures payable, common shares held in other assets	$ 155	155
Junior Subordinated Debt | HF Capital Trust III, variable rate of 3.35%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.35%
Junior Subordinated Debt | HF Capital Trust IV, variable rate of 3.10%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 7,217	7,217
Total junior subordinated debentures payable, common shares held in other assets	$ 217	217
Junior Subordinated Debt | HF Capital Trust IV, variable rate of 3.10%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.10%
Junior Subordinated Debt | HF Capital Trust V, variable rate of 1.83%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 5,310	5,310
Total junior subordinated debentures payable, common shares held in other assets	$ 310	310
Junior Subordinated Debt | HF Capital Trust V, variable rate of 1.83%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.83%
Junior Subordinated Debt | HF Capital Trust VI, variable rate of 1.65%, plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 2,155	2,155
Total junior subordinated debentures payable, common shares held in other assets	$ 155	155
Junior Subordinated Debt | HF Capital Trust VI, variable rate of 1.65%, plus 3 month LIBOR | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.65%
Subordinated Debt
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.875%
Subordinated Debt | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.15%
Subordinated Debt | Fixed to floating rate effective August 2020, 3.150% plus 3 month LIBOR
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 35,000	$ 35,000
Stated interest rate (as a percent)	3.15%

Profit Sharing Plan (Details)

Profit Sharing Plan (Details) $ in Millions	3 Months Ended
	Dec. 31, 2020USD ($)year	Dec. 31, 2019USD ($)
Retirement Benefits [Abstract]
Defined contribution plan, requisite service period	1 year
Defined contribution plan, minimum age requirement (years of age) | year	21
Contributions by the Company | $	$ 1.9	$ 1.7

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1.4	$ 1.6
Tax benefit from compensation expense	0.3	$ 0.4
Share-based compensation, compensation cost not yet recognized	$ 9.7
Share-based compensation, compensation cost not yet recognized, recognition period	2 years 9 months 18 days
Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of vested stock awards	$ 1.9		$ 0.9

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Share and Performance-Based Stock Award Activity (Details) - $ / shares	3 Months Ended	6 Months Ended
	Dec. 31, 2020	Mar. 31, 2020	Sep. 30, 2020
Restricted Shares
Common Shares
Shares, beginning of fiscal year (in shares)	249,180	190,805
Granted (in shares)	152,028	147,282
Vested (in shares)	(79,093)	(84,316)
Forfeited (in shares)	(2,017)	(4,591)
Canceled (in shares)	0	0
Shares, end of period (in shares)	320,098
Vested, but not issuable at end of period (in shares)	87,324		62,992
Weighted-Average Grant Date Fair Value
Shares, beginning of fiscal year (in dollars per share)	$ 32.89	$ 37.20
Granted (in dollars per share)	17.30	30.68
Vested (in dollars per share)	36.28	38.60
Forfeited (in dollars per share)	28.89	36.18
Canceled (in dollars per share)	0	$ 0
Shares, end of period (in dollars per share)	24.67
Vested, but not issuable at end of period (in dollars per share)	$ 29.32		$ 33.98
Performance Shares
Common Shares
Shares, beginning of fiscal year (in shares)	175,740	173,332
Granted (in shares)	115,885	62,278
Vested (in shares)	(25,452)	(54,861)
Forfeited (in shares)	(11,904)	(5,009)
Canceled (in shares)	0	0
Shares, end of period (in shares)	254,269
Vested, but not issuable at end of period (in shares)	5,612		5,612
Weighted-Average Grant Date Fair Value
Shares, beginning of fiscal year (in dollars per share)	$ 33.56	$ 38.50
Granted (in dollars per share)	17.26	40.15
Vested (in dollars per share)	41.07	39.43
Forfeited (in dollars per share)	39.04	37.90
Canceled (in dollars per share)	0	$ 0
Shares, end of period (in dollars per share)	25.12
Vested, but not issuable at end of period (in dollars per share)	$ 18		$ 18

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value Measurements of Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 2,059,615	$ 1,774,626
Derivatives-assets	88,261	98,380
Derivatives-liabilities	324	98
Fair value loans	611,588	655,185
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	25,014	50,152
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,956,431	1,642,780
States and political subdivision securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	52,417	55,580
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,059,615	1,774,626
Derivatives-assets	88,261	98,380
Derivatives-liabilities	324	98
Fair value loans	611,588	655,185
Loan servicing rights	1,063	1,303
Fair value, measurements, recurring | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	25,014	50,152
Fair value, measurements, recurring | U.S. Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	24,703	25,060
Fair value, measurements, recurring | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,956,431	1,642,780
Fair value, measurements, recurring | States and political subdivision securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	52,417	55,580
Fair value, measurements, recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,050	1,054
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	49,717	75,212
Derivatives-assets	0	0
Derivatives-liabilities	0	0
Fair value loans	0	0
Loan servicing rights	0	0
Fair value, measurements, recurring | Level 1 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	25,014	50,152
Fair value, measurements, recurring | Level 1 | U.S. Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	24,703	25,060
Fair value, measurements, recurring | Level 1 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 1 | States and political subdivision securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 1 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,006,232	1,695,617
Derivatives-assets	88,261	98,380
Derivatives-liabilities	324	98
Fair value loans	611,588	655,185
Loan servicing rights	0	0
Fair value, measurements, recurring | Level 2 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 2 | U.S. Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 2 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,956,431	1,642,780
Fair value, measurements, recurring | Level 2 | States and political subdivision securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	48,751	51,783
Fair value, measurements, recurring | Level 2 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,050	1,054
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,666	3,797
Derivatives-assets	0	0
Derivatives-liabilities	0	0
Fair value loans	0	0
Loan servicing rights	1,063	1,303
Fair value, measurements, recurring | Level 3 | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 3 | U.S. Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 3 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Fair value, measurements, recurring | Level 3 | States and political subdivision securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	3,666	3,797
Fair value, measurements, recurring | Level 3 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 0	$ 0

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Changes in Level 3 Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 3,797	$ 4,120
Additions	0	0
Principal paydown	(131)	(134)
Balance, end of period	3,666	3,986
Loan servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	1,303	2,255
Realized and unrealized (loss)	(240)	(201)
Balance, end of period	$ 1,063	$ 2,054

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Mortgage Loans Held-For-Sale, Fair Value Measurement (Details) - Fair value, measurements, nonrecurring - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	$ 8,594	$ 17,991
Impaired loans	275,334	669,968
Mortgage loans held for sale, at lower of cost or fair value	11,638	12,371
Property held for sale	600	600
Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	0	0
Impaired loans	0	0
Mortgage loans held for sale, at lower of cost or fair value	0	0
Property held for sale	0	0
Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	0	0
Impaired loans	0	0
Mortgage loans held for sale, at lower of cost or fair value	11,638	12,371
Property held for sale	0	0
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	8,594	17,991
Impaired loans	275,334	669,968
Mortgage loans held for sale, at lower of cost or fair value	0	0
Property held for sale	$ 600	$ 600

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Valuation Techniques and Significant Unobservable Inputs Used to Measure Level 3 Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Property held for sale	$ 600	$ 600
Fair value, measurements, nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	8,594	17,991
Impaired loans	275,334	669,968
Fair value, measurements, nonrecurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	8,594	17,991
Impaired loans	275,334	$ 669,968
Property held for sale	$ 600

Fair Value Measurements - Sch_3

Fair Value Measurements - Schedule of Fair Values for Balance Sheet Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Liabilities
Unamortized discount on acquired loans	$ 29,200	$ 29,000
Level 1 | Carrying Amount
Assets
Cash and cash equivalents	1,061,796	432,887
Level 1 | Fair Value
Assets
Cash and cash equivalents	1,061,796	432,887
Level 3 | Carrying Amount
Assets
Loans, net, excluding fair valued loans, loans held for sale and impaired loans	8,619,316	8,738,617
Level 3 | Fair Value
Assets
Loans, net, excluding fair valued loans, loans held for sale and impaired loans	8,623,172	8,768,314
Level 2 | Carrying Amount
Liabilities
Time deposits	1,078,580	1,282,978
FHLB advances and other borrowings	120,000	195,000
Securities sold under repurchase agreements	80,355	65,506
Subordinated debentures and subordinated notes payable	108,866	108,832
Level 2 | Fair Value
Liabilities
Time deposits	1,082,378	1,287,814
FHLB advances and other borrowings	129,077	204,715
Securities sold under repurchase agreements	80,355	65,506
Subordinated debentures and subordinated notes payable	$ 93,213	$ 96,424

Earnings per Share - Schedule o

Earnings per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 41,319	$ 43,274
Weighted average common shares outstanding (in shares)	55,119,909	56,377,631
Dilutive effect of stock based compensation (in shares)	127,434	80,336
Weighted average common shares outstanding for diluted earnings per share calculation (in shares)	55,247,343	56,457,967
Basic earnings per share (in dollars per share)	$ 0.75	$ 0.77
Diluted earnings per share (in dollars per share)	$ 0.75	$ 0.77

Earnings per Share - Narrative

Earnings per Share - Narrative (Details) - shares	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Performance Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share (in shares)	115,160	0
Stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share (in shares)	169,539	66,155

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 13,501	$ 15,041
Noninterest income within the scope of other GAAP Topics	647	692
Total noninterest income	14,148	15,733
Service charges and other fees
Disaggregation of Revenue [Line Items]
Revenue	9,624	11,409
Wealth management fees
Disaggregation of Revenue [Line Items]
Revenue	3,029	2,964
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 848	$ 668

Uncategorized Items - gwb-20201

Label	Element	Value
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201602Member	[1]
[1]	Cumulative effect adjustment related to the Company's adoption of ASU 2016-02 and subsequent related ASUs on October 1, 2019.