Great Western Bancorp (GWB) 10-Q 7 May 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2019	May 03, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	Great Western Bancorp, Inc.
Entity Central Index Key	0001613665
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q2
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding (shares)		56,938,553

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Assets
Cash and due from banks	$ 160,852	$ 168,119
Interest-bearing bank deposits	121,786	130,577
Cash and cash equivalents	282,638	298,696
Securities available for sale	1,763,305	1,385,650
Loans, net of unearned discounts and deferred fees, including $36,975 and $42,627 of loans covered by a FDIC loss share agreement at March 31, 2019 and September 30, 2018, respectively, and $835,822 and $865,386 of loans at fair value under the fair value option at March 31, 2019 and September 30, 2018, respectively, and $3,648 and $5,456 of loans held for sale at March 31, 2019 and September 30, 2018, respectively	9,770,911	9,415,924
Allowance for loan and lease losses	(68,003)	(64,540)
Net loans	9,702,908	9,351,384
Premises and equipment, including $3,216 and $1,104 of property held for sale at March 31, 2019 and September 30, 2018, respectively	115,189	113,839
Accrued interest receivable	56,221	58,948
Other repossessed property, including $0 and $131 of property covered by a FDIC loss share agreement at March 31, 2019 and September 30, 2018, respectively	32,450	23,074
Goodwill	739,023	739,023
Cash surrender value of life insurance policies	30,366	30,461
Net deferred tax assets	22,389	30,132
Other assets	85,673	85,601
Total assets	12,830,162	12,116,808
Deposits
Noninterest-bearing	1,824,507	1,842,704
Interest-bearing	8,643,876	7,890,795
Total deposits	10,468,383	9,733,499
Securities sold under agreements to repurchase	62,537	90,907
FHLB advances and other borrowings	275,000	275,000
Subordinated debentures and subordinated notes payable	108,528	108,468
Accrued expenses and other liabilities	63,320	68,383
Total liabilities	10,977,768	10,276,257
Stockholders’ equity
Common stock, $0.01 par value, authorized 500,000,000 shares; 56,938,435 shares issued and outstanding at March 31, 2019 and 58,917,147 shares issued and outstanding at September 30, 2018	569	589
Additional paid-in capital	1,245,657	1,318,457
Retained earnings	614,540	553,014
Accumulated other comprehensive (loss)	(8,372)	(31,509)
Total stockholders' equity	1,852,394	1,840,551
Total liabilities and stockholders' equity	$ 12,830,162	$ 12,116,808

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Assets
Loans covered by a FDIC loss share agreement	$ 36,975	$ 42,627
Loans and written loan commitments at fair value under the fair value option	835,822	865,386
Loan held for sale	3,648	5,456
Property held for sale	3,216	1,104
Property covered under a FDIC loss share agreement	$ 0	$ 131
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)	56,938,435	58,917,147
Common stock, shares outstanding (in shares)	56,938,435	58,917,147

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Interest Income
Loans	$ 123,432	$ 109,993	$ 245,763	$ 217,674
Investment securities	9,957	7,013	19,145	14,055
Federal funds sold and other	497	227	1,039	458
Total interest income	133,886	117,233	265,947	232,187
Interest Expense
Deposits	27,098	12,658	50,892	23,656
FHLB advances and other borrowings	1,923	2,815	3,926	4,978
Subordinated debentures and subordinated notes payable	1,390	1,207	2,760	2,377
Total interest expense	30,411	16,680	57,578	31,011
Net interest income	103,475	100,553	208,369	201,176
Provision for loan and lease losses	7,673	4,900	12,888	9,457
Net interest income after provision for loan and lease losses	95,802	95,653	195,481	191,719
Noninterest Income
Service charges and other fees	10,209	12,047	21,897	25,224
Wealth management fees	2,117	2,335	4,358	4,519
Mortgage banking income, net	991	1,166	2,311	2,826
Net loss on sale of securities	0	(8)	(513)	(9)
Net increase (decrease) in fair value of loans at fair value	14,018	(14,838)	33,234	(23,502)
Net realized and unrealized (loss) gain on derivatives	(11,032)	14,282	(29,348)	21,509
Other	1,920	3,758	3,004	4,849
Total noninterest income	18,223	18,742	34,943	35,416
Noninterest Expense
Salaries and employee benefits	34,537	33,672	69,307	66,539
Data processing and communication	5,964	9,190	11,242	16,074
Occupancy and equipment	5,539	5,290	10,665	10,138
Professional fees	3,970	4,027	7,258	8,267
Advertising	1,216	1,121	2,154	2,181
Net loss on repossessed property and other related expenses	404	1,000	3,467	1,214
Other	4,950	4,844	9,593	9,599
Total noninterest expense	56,580	59,144	113,686	114,012
Income before income taxes	57,445	55,251	116,738	113,123
Provision for income taxes	12,934	14,719	26,441	43,361
Net income	$ 44,511	$ 40,532	$ 90,297	$ 69,762
Basic earnings per common share
Weighted average shares outstanding (in shares)	56,994,817	58,941,315	57,484,838	58,921,972
Earnings per share (in dollars per share)	$ 0.78	$ 0.69	$ 1.57	$ 1.18
Diluted earnings per common share
Weighted average shares outstanding (in shares)	57,074,674	59,146,117	57,556,984	59,116,923
Diluted earnings per share (in dollars per share)	$ 0.78	$ 0.69	$ 1.57	$ 1.18
Dividends per share
Dividends paid	$ 14,235	$ 11,780	$ 28,771	$ 23,550
Dividends per share (in dollars per share)	$ 0.25	$ 0.20	$ 0.50	$ 0.40

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income		$ 44,511	$ 40,532	$ 90,297	$ 69,762
Securities available for sale:
Net unrealized holding gain (loss) arising during the period		11,523	(12,425)	30,192	(21,070)
Reclassification adjustment for net loss realized in net income		0	8	513	9
Income tax (expense) benefit		(2,839)	3,062	(7,568)	6,345
Net change in unrealized gain (loss) on securities available for sale		8,684	(9,355)	23,137	(14,716)
Net unrealized holding gain arising during the period	[1]	0	0	0	145
Income tax expense	[1]	0	0	0	(55)
Net change in defined benefit pension plan obligation	[1]	0	0	0	90
Other comprehensive income (loss), net of tax		8,684	(9,355)	23,137	(14,626)
Comprehensive income		$ 53,195	$ 31,177	$ 113,434	$ 55,136
[1]	The Company's Board of Directors voted to terminate the defined benefit pension plan ("Pension Plan") effective February 1, 2018. Transfer of all Pension Plan assets, liabilities and administrative responsibilities were completed as of September 30, 2018.

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Common Stock Par Value	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive (Loss)
Beginning balance at Sep. 30, 2017		$ 1,755,000	$ 588	$ 1,314,039	$ 445,747	$ (5,374)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		40,532			40,532
Other comprehensive (loss), net of tax		(9,355)				(9,355)
Comprehensive income		31,177
Stock-based compensation, net of tax		1,428	1	1,427
Reclassification due to adoption of ASU 2018-02	[1]				2,353	(2,353)
Common stock cash dividends		(11,780)			(11,780)
Ending balance at Dec. 31, 2017		1,767,873	588	1,314,723	463,207	(10,645)
Beginning balance at Sep. 30, 2017		1,755,000	588	1,314,039	445,747	(5,374)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		69,762			69,762
Other comprehensive (loss), net of tax		(14,626)				(14,626)
Comprehensive income		55,136
Stock-based compensation, net of tax		2,112	1	2,111
Reclassification due to adoption of ASU 2018-02	[1]				2,353	(2,353)
Common stock cash dividends		(23,550)			(23,550)
Ending balance at Mar. 31, 2018		1,788,698	589	1,316,150	494,312	(22,353)
Beginning balance at Dec. 31, 2017		1,767,873	588	1,314,723	463,207	(10,645)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		40,532
Other comprehensive (loss), net of tax		(9,355)
Comprehensive income		31,177
Common stock cash dividends		(11,780)
Ending balance at Mar. 31, 2018		1,788,698	589	1,316,150	494,312	(22,353)
Beginning balance at Sep. 30, 2018		1,840,551	589	1,318,457	553,014	(31,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		90,297			90,297
Other comprehensive (loss), net of tax		23,137				23,137
Comprehensive income		113,434
Stock-based compensation, net of tax		1,839	1	1,838
Common stock cash dividends		(28,771)			(28,771)
Repurchase common stock		(74,659)	(21)	(74,638)
Ending balance at Mar. 31, 2019		1,852,394	569	1,245,657	614,540	(8,372)
Beginning balance at Dec. 31, 2018		1,812,008	568	1,244,232	584,264	(17,056)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		44,511			44,511
Other comprehensive (loss), net of tax		8,684				8,684
Comprehensive income		53,195
Stock-based compensation, net of tax		1,426	1	1,425
Common stock cash dividends		(14,235)			(14,235)
Ending balance at Mar. 31, 2019		$ 1,852,394	$ 569	$ 1,245,657	$ 614,540	$ (8,372)
[1]	Reclassification due to adoption of ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See Note 2, New Accounting Pronouncements and Note 15, Income Taxes, for additional information.

Consolidated Statement of Sto_2

Consolidated Statement of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Cash dividends paid on common stock (in dollars per share)	$ 0.25	$ 0.2	$ 0.5	$ 0.4

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net income	$ 90,297	$ 69,762
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,916	5,943
Amortization of FDIC indemnification asset	853	1,689
Net loss on sale of securities and other assets	2,974	2,143
Net gain on sale of loans	(2,724)	(3,314)
Provision for loan and lease losses	12,888	9,457
Reversal of loan servicing rights loss	0	(71)
Stock-based compensation	1,839	2,112
Originations of residential real estate loans held for sale	(98,875)	(112,731)
Proceeds from sales of residential real estate loans held for sale	103,407	121,072
Net deferred income taxes	688	17,215
Changes in:
Accrued interest receivable	2,727	3,823
Other assets	22,116	423
Accrued interest payable and other liabilities	(27,768)	(18,336)
Net cash provided by operating activities	114,338	99,187
Investing activities
Purchase of securities available for sale	(541,872)	(110,741)
Proceeds from sales of securities available for sale	97,212	25,206
Proceeds from maturities of securities available for sale	94,926	122,436
Net increase in loans	(383,665)	(392,109)
Recovery (payment) of covered losses from FDIC indemnification claims	43	(419)
Purchase of premises and equipment	(5,953)	(3,297)
Proceeds from sale of premises and equipment	299	4,565
Proceeds from sale of repossessed property	6,593	2,050
Purchase of FHLB stock	(46,948)	(30,420)
Proceeds from redemption of FHLB stock	47,030	34,251
Net cash used in investing activities	(732,335)	(348,478)
Financing activities
Net increase in deposits	734,966	409,509
Net decrease in securities sold under agreements to repurchase and other short-term borrowings	(28,370)	(29,345)
Proceeds from FHLB advances and other long-term borrowings	465,000	419,999
Repayments on FHLB advances and other long-term borrowings	(465,000)	(512,200)
Common stock repurchased	(74,659)	0
Taxes paid related to net share settlement of equity awards	(1,227)	(3,769)
Dividends paid	(28,771)	(23,550)
Net cash provided by financing activities	601,939	260,644
Net (decrease) increase in cash and cash equivalents	(16,058)	11,353
Cash and cash equivalents, beginning of period	298,696	360,396
Cash and cash equivalents, end of period	282,638	371,749
Supplemental disclosure of cash flow information
Cash payments for interest	52,551	29,251
Cash payments for income taxes	19,113	23,980
Supplemental disclosure of noncash investing and financing activities
Loans transferred to repossessed properties	$ (17,919)	$ (11,005)

Nature of Operations and Summar

Nature of Operations and Summary of Significant Policies	6 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Nature of Operations and Summary of Significant Policies	1. 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 . 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. Substantially all of the Company’s income is generated from banking operations. Basis of Presentation The accompanying unaudited consolidated interim financial statements have been prepared in accordance with U.S. 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, 2018 , 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 U.S. 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 certain ASUs as of October 1, 2018, the following significant accounting policies have been updated from those disclosed in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2018 . Revenue Recognition We adopted ASU 2014-09, " Revenue from Contracts with Customers (Topic 606) " and subsequent related ASUs effective October 1, 2018 using the modified retrospective approach, which establishes principles for reporting information about the nature, amount, timing and uncertainty of revenue and cash flows arising from the Company's contracts to provide goods or services to 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 our revenue-generating transactions are not subject to ASC Topic 606, including revenue generated from financial instruments, such as our loans, letters of credit, derivatives and investment securities, as well as revenue related to our mortgage servicing activities, as these activities are subject to other GAAP discussed elsewhere within our disclosures and in "Note 1. Nature of Operations and Summary of Significant Policies ," in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2018 . Descriptions of our revenue-generating activities that are within the scope of ASC Topic 606, which are presented in our 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 March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Noninterest income Service charges and other fees $ 10,209 $ 12,047 $ 21,897 $ 25,224 Wealth management fees 2,117 2,335 4,358 4,519 Other 1,118 3,351 1,700 4,002 Noninterest income from contracts with customers within the scope of ASC Topic 606 ¹ 13,444 17,733 27,955 33,745 Noninterest income within the scope of other GAAP Topics ² 4,779 1,009 6,988 1,671 Total noninterest income $ 18,223 $ 18,742 $ 34,943 $ 35,416 1 Amounts for periods after October 1, 2018 are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers , except for out of scope amounts. Amounts for periods prior to October 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition , and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers . 2 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. At March 31, 2019 , the Company does not have any material contract assets, liabilities, or other receivables recorded on its consolidated balance sheets relating to its revenue streams within the scope of ASC Topic 606. Additionally, the Company's contracts generally do not contain terms that require significant judgment to determine the amount of revenue to recognize. Practical expedients The Company has elected the practical expedient to exclude the disclosure of unsatisfied performance obligations for contracts with an original expected length of one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which the Company has the right to invoice for services performed. The Company recognizes incremental costs of obtaining those contracts as an expense when incurred. 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 other material events or transactions that would require recognition in the consolidated financial statements or disclosure in the notes to the consolidated financial statements. On April 25, 2019 , the Board of Directors of the Company declared a dividend of $0.30 per common share payable on May 24, 2019 to stockholders of record as of close of business on May 10, 2019 .

New Accounting Pronouncements

New Accounting Pronouncements	6 Months Ended
	Mar. 31, 2019
Accounting Changes and Error Corrections [Abstract]
New Accounting Pronouncements	2. New Accounting Standards Accounting Standards Adopted in Fiscal Year 2019 In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , which implements a more robust framework that clarifies the principles for recognizing revenue and gives greater consistency and comparability in revenue recognition practices. In the new framework, an entity recognizes revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for goods or services. The new model requires the identification of performance obligations included in the contract with customers, a determination of the transaction price and an allocation of the price to those performance obligations. The entity recognizes revenue when performance obligations are satisfied. In August 2015, the FASB issued ASU 2015-14, which deferred the effective date of ASU 2014-09 to annual reporting periods beginning after December 15, 2017. In March 2016, the FASB issued ASU 2016-08, which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU 2016-10, which clarifies guidance pertaining to the identification of performance obligations and the licensing implementation. In May 2016, the FASB issued ASU 2016-11 and 2016-12, which further clarify guidance and provide practical expedients related to the adoption of ASU 2014-09. In December 2016, the FASB issued ASU 2016-20, which made technical corrections and improvements to the previous ASUs issued. The standard permits the use of either the retrospective or cumulative effect transition method. The standard, along with subsequent guidance from FASB, lists several items that are specifically out of scope for ASU 2014-09, including but not limited to core interest income, derivative instruments, investments, and loan origination fees. The Company adopted this standard and subsequent related ASUs October 1, 2018 using the modified retrospective method. Furthermore, the Company prospectively changed the presentation of direct expenses, including reward costs, associated with credit and debit card interchange income previously included in data processing and communication expense which are now netted against interchange income in service charges and other fees, which is included in noninterest income on the consolidated statements of income. Brokerage charges previously included in professional fees are now netted against wealth management fees, which is included in noninterest income on the consolidated statements of income. The net quantitative impact of these presentation changes decreased both revenue and expenses by $2.0 million and $3.7 million for the three and six months ended March 31, 2019 ; however, these presentation changes did not have an impact on net income. Prior period balances have not been restated to reflect these presentation changes. There were no significant cumulative effect adjustments as a result of implementation as our current revenue recognition policies generally conform with the principals in ASC Topic 606. For additional information, see "Note 1. Nature of Operations and Summary of Significant Policies ." Accounting Standards Not Yet Adopted in Fiscal Year 2019 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 our consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities , which amends the hedge accounting recognition and presentation requirements in ASC 815 to improve the transparency and understandability of information conveyed to financial statement users about an entity’s risk management activities to better align the entity’s financial reporting for hedging relationships with those risk management activities and to reduce the complexity of and simplify the application of hedge accounting. ASU 2017-12 is to be applied to all existing hedging relationships on the date of adoption and will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted in any interim period, with the effect of adoption reflected as of the beginning of the fiscal year of adoption. The Company is currently evaluating the potential impact of ASU 2017-12 on our consolidated financial statements and does not expect to early adopt this standard. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which addresses timelier recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. ASU 2016-13 requires institutions to measure all expected credit losses related to financial assets measured at amortized costs 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 current expected credit loss (CECL) model. ASU 2016-13 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. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments, Credit Losses , which made technical corrections and improvements to the previous ASU issued. These ASUs will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted after December 15, 2018. The amendment requires the use of the modified retrospective approach for adoption. The Company continues to make progress on the implementation plan and has submitted historical data to third party vendor to start making necessary changes to our existing credit loss estimation process. The Company does not expect to early adopt this standard and is currently evaluating the potential impact on our consolidated financial statements; however, since the magnitude of the anticipated change in the allowance for credit losses will be impacted by economic conditions and trends in the Company’s portfolio at the time of adoption, the quantitative impact cannot yet be reasonably estimated. In February 2016, the FASB issued ASU 2016-02 , Leases (Topic 842) , which requires that lessees recognize the assets and liabilities arising from leases on the balance sheet and disclosing key information about leasing arrangements. Lessees will be required to recognize an obligation for future lease payments measured on a discounted basis and a related right-of-use asset. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model and ASC Topic 606, Revenue from Contracts with Customers . In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases , and ASU 2018-11, Leases (Topic 842), Targeted Improvements , which made technical corrections and improvements to the previous ASU issued. In December 2018, the FASB issued ASU 2018-20, Leases (Topic 842): Narrow-Scope Improvements for Lessors , which allows lessors to exclude sales tax from consideration of the contract through a policy election and clarifies treatment of certain lessor costs and variable payments for contracts with lease and nonlease components. These ASUs will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The guidance will be effective with respect to the Company beginning fiscal year 2020. The Company has a project team working on the implementation plan, is currently reviewing all existing lease agreements for which the amended guidance is to be applied, is in the process of determining which practical expedients will be elected for transition and is currently evaluating the potential impact on our consolidated financial statements.

Securities Available for Sale

Securities Available for Sale	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 U.S. Treasury securities $ 93,696 $ 419 $ (296 ) $ 93,819 Mortgage-backed securities: Government National Mortgage Association 491,888 1,811 (9,909 ) 483,790 Federal Home Loan Mortgage Corporation 438,605 3,697 (2,839 ) 439,463 Federal National Mortgage Association 303,643 1,268 (2,386 ) 302,525 Small Business Assistance Program 382,165 514 (2,841 ) 379,838 States and political subdivision securities 63,400 151 (681 ) 62,870 Other 1,006 — (6 ) 1,000 Total $ 1,774,403 $ 7,860 $ (18,958 ) $ 1,763,305 Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated (dollars in thousands) As of September 30, 2018 U.S. Treasury securities $ 168,394 $ — $ (1,222 ) $ 167,172 Mortgage-backed securities: Government National Mortgage Association 442,458 35 (16,335 ) 426,158 Federal Home Loan Mortgage Corporation 297,380 — (7,055 ) 290,325 Federal National Mortgage Association 188,192 — (6,081 ) 182,111 Small Business Assistance Program 260,458 — (9,345 ) 251,113 States and political subdivision securities 69,566 4 (1,795 ) 67,775 Other 1,006 — (10 ) 996 Total $ 1,427,454 $ 39 $ (41,843 ) $ 1,385,650 The amortized cost and approximate fair value of debt securities available for sale as of March 31, 2019 and September 30, 2018 , 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. March 31, 2019 September 30, 2018 Amortized Estimated Amortized Estimated (dollars in thousands) Due in one year or less $ 36,309 $ 36,153 $ 111,842 $ 111,221 Due after one year through five years 111,862 111,756 114,920 113,069 Due after five years through ten years 8,803 8,658 11,076 10,535 Due after ten years 122 122 122 122 157,096 156,689 237,960 234,947 Mortgage-backed securities 1,616,301 1,605,616 1,188,488 1,149,707 Securities without contractual maturities 1,006 1,000 1,006 996 Total $ 1,774,403 $ 1,763,305 $ 1,427,454 $ 1,385,650 Proceeds from sales of securities available for sale were $0.0 million and $97.2 million for the three and six months ended March 31, 2019 and $25.0 million and $25.2 million for the three and six months ended March 31, 2018 , respectively. No gross gains (pre-tax) were realized on the sales for the three and six months ended March 31, 2019 and 2018 using the specific identification method. Negligible gross losses (pre-tax) were realized on the sales for the three months ended March 31, 2019 and 2018 , and $0.5 million and negligible gross losses (pre-tax) were realized on the sales for each of the six months ended March 31, 2019 and 2018 , respectively, using the specific identification method. The Company recognized no other-than-temporary impairment for the three and six months ended March 31, 2019 and 2018 . Securities with an estimated fair value of approximately $945.9 million and $787.4 million at March 31, 2019 and September 30, 2018 , 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 62% and 98% of the Company’s investment portfolio at estimated fair value at March 31, 2019 and September 30, 2018 , 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 temporary. As the Company does not intend to sell the securities and it is not more-likely-than-not the Company will be required to sell the securities before the recovery of their amortized cost basis, which may be maturity, the Company does not consider the securities to be other-than-temporarily impaired at March 31, 2019 or September 30, 2018 . 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 March 31, 2019 U.S. Treasury securities $ — $ — $ 44,232 $ (296 ) $ 44,232 $ (296 ) Mortgage-backed securities 126,015 (468 ) 865,274 (17,507 ) 991,289 (17,975 ) States and political subdivision securities — — 49,649 (681 ) 49,649 (681 ) Other — — 1,000 (6 ) 1,000 (6 ) Total $ 126,015 $ (468 ) $ 960,155 $ (18,490 ) $ 1,086,170 $ (18,958 ) Less than 12 months 12 months or more Total Estimated Unrealized Estimated Unrealized Estimated Unrealized (dollars in thousands) As of September 30, 2018 U.S. Treasury securities $ 167,172 $ (1,222 ) $ — $ — $ 167,172 $ (1,222 ) Mortgage-backed securities 416,677 (8,427 ) 709,387 (30,389 ) 1,126,064 (38,816 ) States and political subdivision securities 23,534 (250 ) 42,282 (1,545 ) 65,816 (1,795 ) Other 996 (10 ) — — 996 (10 ) Total $ 608,379 $ (9,909 ) $ 751,669 $ (31,934 ) $ 1,360,048 $ (41,843 ) As of March 31, 2019 and September 30, 2018 , the Company had 293 and 390 securities, respectively, in an unrealized loss position.

Loans

Loans	6 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Loans	Loans The following table presents the composition of loans as of March 31, 2019 and September 30, 2018 . March 31, September 30, 2019 2018 (dollars in thousands) Commercial real estate $ 5,049,792 $ 4,629,330 Agriculture 2,121,872 2,182,688 Commercial non-real estate 1,721,095 1,699,987 Residential real estate 815,212 837,569 Consumer 44,504 49,689 Other 46,163 46,487 Ending balance 9,798,638 9,445,750 Less: Unamortized discount on acquired loans (15,255 ) (18,283 ) Unearned net deferred fees and costs and loans in process (12,472 ) (11,543 ) Total $ 9,770,911 $ 9,415,924 The loan segments above include loans covered by a FDIC loss sharing agreement totaling $37.0 million and $42.6 million as of March 31, 2019 and September 30, 2018 , respectively, residential real estate loans held for sale totaling $3.6 million and $5.5 million at March 31, 2019 and September 30, 2018 , respectively, and $835.8 million and $865.4 million of loans accounted for at fair value at March 31, 2019 and September 30, 2018 , respectively. Unearned net deferred fees and costs totaled $13.5 million and $13.0 million as of March 31, 2019 and September 30, 2018 , respectively. Loans in process represent loans that have been funded as of the balance sheet dates but not classified into a loan category and loan payments received as of the balance sheet dates that have not been applied to individual loan accounts. Loans in process totaled $(1.0) million and $(1.5) million at March 31, 2019 and September 30, 2018 , respectively. Loans guaranteed by agencies of the U.S. government totaled $164.5 million and $168.6 million at March 31, 2019 and September 30, 2018 , respectively. Principal balances of residential real estate loans sold totaled $46.8 million and $67.6 million for the three months March 31, 2019 and 2018 , respectively, and $100.7 million and $117.8 million for the six months ended March 31, 2019 and 2018 , respectively. Nonaccrual Interest income on loans is accrued daily on the outstanding balances. A loan is placed on nonaccrual status and accrual of interest is discontinued when principal or interest becomes 90 days past due unless it is well secured and is in the process of collection, or earlier when concern exists as to the ultimate collectibility of principal or interest. When loans are placed on nonaccrual status, 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. The following table presents the Company’s nonaccrual loans at March 31, 2019 and September 30, 2018 , excluding ASC 310-30 loans. Loans greater than 90 days past due and still accruing interest as of March 31, 2019 and September 30, 2018 , were $0.0 million and $0.2 million , respectively. March 31, September 30, 2019 2018 (dollars in thousands) Nonaccrual loans Commercial real estate $ 17,929 $ 22,871 Agriculture 91,771 107,198 Commercial non-real estate 6,868 6,887 Residential real estate 2,499 3,549 Consumer 87 61 Total $ 119,154 $ 140,566 Credit Quality Information The Company assigns all non-consumer loans a credit quality risk rating. These ratings are Pass, Watch, Substandard, Doubtful, and Loss. Loans with a Pass and Watch rating represent those loans not classified on the Company’s rating scale as problem credits, with loans with a Watch rating being monitored and updated at least quarterly by management. Substandard loans are those where a well-defined weakness has been identified that may put full collection of contractual debt at risk. Doubtful loans are those where a well-defined weakness has been identified and a loss of contractual debt is probable. Substandard and doubtful loans are monitored and updated monthly. All loan risk ratings are updated and monitored on a continuous basis. 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, standard credit scoring systems are used to assess credit risks of consumer loans. The following table presents the composition of the loan portfolio by internally assigned grade as of March 31, 2019 and September 30, 2018 . This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . As of March 31, 2019 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer ¹ Other Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,455,347 $ 1,584,602 $ 1,512,883 $ 762,495 $ 44,013 $ 46,163 $ 8,405,503 Watchlist 47,424 199,585 32,402 5,450 102 — 284,963 Substandard 32,938 158,061 20,926 6,435 210 — 218,570 Doubtful 61 137 1,325 29 — — 1,552 Loss — — — — — — — Ending balance 4,535,770 1,942,385 1,567,536 774,409 44,325 46,163 8,910,588 Loans covered by a FDIC loss sharing agreement — — — 36,975 — — 36,975 Total $ 4,535,770 $ 1,942,385 $ 1,567,536 $ 811,384 $ 44,325 $ 46,163 $ 8,947,563 1 The Company generally does not risk rate residential real estate or consumer 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 loans. As of September 30, 2018 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer ¹ Other Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,108,314 $ 1,610,291 $ 1,401,418 $ 779,610 $ 48,979 $ 46,487 $ 7,995,099 Watchlist 53,150 239,392 19,503 4,548 322 — 316,915 Substandard 41,184 137,205 20,117 6,366 159 — 205,031 Doubtful 93 2 2,277 37 — — 2,409 Loss — — — — — — — Ending balance 4,202,741 1,986,890 1,443,315 790,561 49,460 46,487 8,519,454 Loans covered by a FDIC loss sharing agreement — — — 42,627 — — 42,627 Total $ 4,202,741 $ 1,986,890 $ 1,443,315 $ 833,188 $ 49,460 $ 46,487 $ 8,562,081 1 The Company generally does not risk rate residential real estate or consumer 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 loans. Past Due Loans The following table presents the Company’s past due loans at March 31, 2019 and September 30, 2018 . This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Current Total Financing Receivables (dollars in thousands) As of March 31, 2019 Commercial real estate $ 3,051 $ 95 $ 5,519 $ 8,665 $ 4,527,105 $ 4,535,770 Agriculture 11,558 8,985 37,075 57,618 1,884,767 1,942,385 Commercial non-real estate 2,161 4,134 3,452 9,747 1,557,789 1,567,536 Residential real estate 2,341 700 803 3,844 770,565 774,409 Consumer 208 15 — 223 44,102 44,325 Other — — — — 46,163 46,163 Ending balance 19,319 13,929 46,849 80,097 8,830,491 8,910,588 Loans covered by a FDIC loss sharing agreement 1,955 78 214 2,247 34,728 36,975 Total $ 21,274 $ 14,007 $ 47,063 $ 82,344 $ 8,865,219 $ 8,947,563 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Current Total Financing Receivables (dollars in thousands) As of September 30, 2018 Commercial real estate $ 920 $ 551 $ 9,135 $ 10,606 $ 4,192,135 $ 4,202,741 Agriculture 1,243 2,042 51,579 54,864 1,932,026 1,986,890 Commercial non-real estate 551 16 4,068 4,635 1,438,680 1,443,315 Residential real estate 913 200 1,747 2,860 787,701 790,561 Consumer 83 47 1 131 49,329 49,460 Other — — — — 46,487 46,487 Ending balance 3,710 2,856 66,530 73,096 8,446,358 8,519,454 Loans covered by a FDIC loss sharing agreement 30 233 471 734 41,893 42,627 Total $ 3,740 $ 3,089 $ 67,001 $ 73,830 $ 8,488,251 $ 8,562,081 Impaired Loans The following table presents the Company’s impaired loans. This table excludes purchased credit impaired loans and loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . March 31, 2019 September 30, 2018 Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance (dollars in thousands) Impaired loans: With an allowance recorded: Commercial real estate $ 22,058 $ 22,102 $ 2,258 $ 25,136 $ 25,223 $ 3,668 Agriculture 67,476 81,601 14,281 60,053 76,874 9,590 Commercial non-real estate 14,214 16,933 3,338 14,177 17,241 4,508 Residential real estate 3,093 3,678 1,562 4,509 5,153 2,210 Consumer 209 213 123 160 165 61 Total impaired loans with an allowance recorded 107,050 124,527 21,562 104,035 124,656 20,037 With no allowance recorded: Commercial real estate 10,595 50,487 — 15,764 58,141 — Agriculture 92,021 102,968 — 77,172 80,355 — Commercial non-real estate 8,669 17,809 — 8,905 18,047 — Residential real estate 3,539 5,969 — 2,177 4,574 — Consumer — 117 — 1 118 — Total impaired loans with no allowance recorded 114,824 177,350 — 104,019 161,235 — Total impaired loans $ 221,874 $ 301,877 $ 21,562 $ 208,054 $ 285,891 $ 20,037 The following table presents the average recorded investment on impaired loans and interest income recognized on impaired loans for the three and six months ended March 31, 2019 and 2018 . Three Months Ended Six Months Ended March 31, 2019 March 31, 2018 March 31, 2019 March 31, 2018 Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status (dollars in thousands) Commercial real estate $ 34,475 $ 345 $ 66,577 $ 477 $ 36,616 $ 697 $ 56,875 $ 2,053 Agriculture 151,021 2,203 121,062 1,189 146,423 3,202 124,200 2,171 Commercial non-real estate 22,556 312 30,350 325 22,731 678 30,878 776 Residential real estate 6,724 93 7,578 116 6,711 182 7,636 281 Consumer 237 6 238 4 212 11 256 8 Total $ 215,013 $ 2,959 $ 225,805 $ 2,111 $ 212,693 $ 4,770 $ 219,845 $ 5,289 Valuation adjustments made to repossessed properties totaled $0.1 million and $0.7 million for the three months ended March 31, 2019 and 2018 , respectively, and $2.0 million and $0.7 million for the six months ended March 31, 2019 and 2018 , respectively. The adjustments are included in net loss on repossessed property and other related expenses in noninterest expense. Troubled Debt Restructurings Included in certain loan categories in the impaired loans are TDRs that were classified as impaired. These TDRs do not include purchased credit impaired loans. When the Company grants concessions to borrowers such as reduced interest rates or extensions of loan periods that would not be considered other than because of borrowers’ financial difficulties, the modification is considered a TDR. Specific reserves included in the allowance for loan and lease losses for TDRs were $7.4 million and $9.2 million at March 31, 2019 and September 30, 2018 , respectively. There were $0.6 million of commitments to lend additional funds to borrowers whose loans were modified in a TDR as of March 31, 2019 and $0.3 million commitments to lend additional funds to borrowers whose loans were modified in a TDR as of September 30, 2018 . The following table presents the recorded value of the Company’s TDR balances as of March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Accruing Nonaccrual Accruing Nonaccrual (dollars in thousands) Commercial real estate $ 1,930 $ 1,068 $ 2,649 $ 2,616 Agriculture 12,377 46,592 13,248 73,741 Commercial non-real estate 2,498 705 3,420 656 Residential real estate 347 115 389 143 Consumer 91 61 77 — Total $ 17,243 $ 48,541 $ 19,783 $ 77,156 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 and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Recorded Investment Recorded Investment Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Commercial real estate — $ — $ — — $ — $ — — $ — $ — — $ — $ — Agriculture — — — 2 6,073 6,073 — $ — — 2 6,073 6,073 Commercial non-real estate — — — — — — — $ — — — — — Residential real estate — — — — — — — — — — — — Consumer — — — 1 73 73 1 $ 89 89 1 73 73 Total accruing — $ — $ — 3 $ 6,146 $ 6,146 1 $ 89 $ 89 3 $ 6,146 $ 6,146 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — — — — — — — The following table presents a summary of all nonaccruing loans restructured in TDRs for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Recorded Investment Recorded Investment Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Commercial real estate — $ — $ — — $ — $ — — $ — $ — — $ — $ — Agriculture — — — 6 8,374 8,374 — $ — — 6 8,374 8,374 Commercial non-real estate — — — — — — — $ — — — — — Residential real estate — — — — — — — — — — — — Consumer — — — — — — — $ — — — — — Total nonaccruing — $ — $ — 6 $ 8,374 $ 8,374 — $ — $ — 6 $ 8,374 $ 8,374 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — — — — — — — The following table presents loans that were modified as TDRs within the previous 12 months and for which there was a payment default for the three and six months ended March 31, 2019 and 2018 , respectively. Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Loans Recorded Investment (dollars in thousands) Commercial real estate — $ — — $ — — $ — 1 $ 1,012 Agriculture — — 3 4,264 — — 4 5,011 Commercial non-real estate — — — — — — — — Residential real estate — — — — — — — — Consumer — — — — — — — — Total — $ — 3 $ 4,264 — $ — 5 $ 6,023 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. There were $0.0 million and $0.1 million for the three months ended March 31, 2019 and 2018 , respectively, and $0.0 million and $0.6 million for the six months ended March 31, 2019 and 2018 , respectively, of loans removed from TDR status as they were restructured at market terms and are performing.

Allowance for Loan and Lease Lo

Allowance for Loan and Lease Losses	6 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Allowance for Loan and Lease Losses	Allowance for Loan and Lease Losses The allowance for loan and lease losses is determined 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 Company considers the uncertainty related to certain industry sectors and the extent of credit exposure to specific borrowers within the portfolio. In addition, consideration is given to concentration risks associated with the various loan portfolios and current economic conditions that might impact the portfolio. The Company also considers changes, if any, in underwriting activities, the loan portfolio composition (including product mix and geographic, industry, or customer-specific concentrations), trends in loan performance, the level of allowance coverage relative to similar banking institutions and macroeconomic factors, such as changes in unemployment rates, gross domestic product, and consumer bankruptcy filings. Changes to the allowance for loan and lease losses are made by charges to the provision for loan and lease losses, which is reflected on the consolidated statements of income. Past due status is monitored as an indicator of credit deterioration. Loans that are 90 days or more past due are put on nonaccrual status unless a repayment is eminent. Loans deemed to be uncollectible are charged off against the allowance for loan and lease losses. Recoveries of amounts previously charged-off are credited to the allowance for loan and lease losses. The allowance for loan and lease losses consist of reserves for probable losses that have been identified related to specific borrowing relationships that are individually evaluated for impairment ("specific reserve"), as well as probable losses inherent in our loan portfolio that are not specifically identified ("collective reserve"). The specific reserve relates to impaired loans. A loan is impaired when, based on current information and events, it is probable the Company will be unable to collect all amounts due (interest as well as principal) according to the contractual terms of the loan agreement. Specific reserves are determined on a loan-by-loan basis based on management’s best estimate of the Company's exposure, given the current payment status of the loan, the present value of expected payments, and the value of any underlying collateral. Impaired loans also include loans modified in troubled debt restructurings. Generally, the impairment related to troubled debt restructurings is measured based on the fair value of the collateral, less cost to sell, or the present value of expected payments relative to the unpaid principal balance. If the impaired loan is identified as collateral dependent, then the fair value of the collateral method of measuring the amount of the impairment is utilized. This method requires obtaining an independent appraisal of the collateral and reducing the appraised value by applying a discount factor to the appraised value, if necessary, and including costs to sell. Management’s estimate for collective reserves reflects losses incurred in the loan portfolio as of the consolidated balance sheet reporting date. Incurred loss estimates primarily are based on historical loss experience and portfolio mix. Incurred loss estimates may be adjusted for qualitative factors such as current economic conditions and current portfolio trends including credit quality, concentrations, aging of the portfolio, and/or significant policy and underwriting changes. The following tables present the Company’s allowance for loan and lease losses roll forward for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, 2019 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance January 1, 2019 $ 16,348 $ 31,785 $ 12,093 $ 4,611 $ 430 $ 926 $ 66,193 Charge-offs (75 ) (5,767 ) (110 ) (310 ) (85 ) (249 ) (6,596 ) Recoveries 162 199 104 125 44 99 733 Provision (855 ) 7,508 962 (344 ) (15 ) 150 7,406 Impairment of ASC 310-30 loans 23 — — 244 — — 267 Ending balance March 31, 2019 $ 15,603 $ 33,725 $ 13,049 $ 4,326 $ 374 $ 926 $ 68,003 Three Months Ended March 31, 2018 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance January 1, 2018 $ 15,995 $ 24,750 $ 16,434 $ 5,475 $ 307 $ 1,062 $ 64,023 Charge-offs (1,268 ) (783 ) (1,605 ) (20 ) (62 ) (557 ) (4,295 ) Recoveries 61 125 88 27 20 190 511 Provision 4,077 152 813 (341 ) 14 281 4,996 Impairment (improvement) of ASC 310-30 loans 49 (115 ) — (30 ) — — (96 ) Ending balance March 31, 2018 $ 18,914 $ 24,129 $ 15,730 $ 5,111 $ 279 $ 976 $ 65,139 Six Months Ended March 31, 2019 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance October 1, 2018 $ 16,777 $ 28,121 $ 13,610 $ 4,749 $ 257 $ 1,026 $ 64,540 Charge-offs (946 ) (7,028 ) (1,471 ) (642 ) (334 ) (394 ) (10,815 ) Recoveries 259 357 228 287 128 131 1,390 Provision (68 ) 12,275 682 (369 ) 323 163 13,006 (Improvement) impairment of ASC 310-30 loans (419 ) — — 301 — — (118 ) Ending balance March 31, 2019 $ 15,603 $ 33,725 $ 13,049 $ 4,326 $ 374 $ 926 $ 68,003 Six Months Ended March 31, 2018 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance January 1, 2018 $ 16,941 $ 25,757 $ 14,114 $ 5,347 $ 329 $ 1,015 $ 63,503 Charge-offs (1,597 ) (2,981 ) (2,844 ) (275 ) (116 ) (1,091 ) (8,904 ) Recoveries 209 172 209 117 42 334 1,083 Provision 3,322 1,296 4,251 (11 ) 24 718 9,600 Impairment (improvement) of ASC 310-30 loans 39 (115 ) — (67 ) — — (143 ) Ending balance March 31, 2018 $ 18,914 $ 24,129 $ 15,730 $ 5,111 $ 279 $ 976 $ 65,139 The following tables provide details regarding the allowance for loan and lease losses and balance by type of allowance as of March 31, 2019 and September 30, 2018 . These tables are presented net of unamortized discount on acquired loans and excludes loans of $835.8 million measured at fair value, loans held for sale of $3.6 million , and guaranteed loans of $153.5 million for March 31, 2019 and loans measured at fair value of $865.4 million , loans held for sale of $5.5 million , and guaranteed loans of $160.3 million for September 30, 2018 . As of March 31, 2019 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Allowance for loan and lease losses Individually evaluated for impairment $ 2,258 $ 14,281 $ 3,338 $ 1,562 $ 123 $ — $ 21,562 Collectively evaluated for impairment 13,085 19,179 9,711 2,201 251 926 45,353 ASC 310-30 loans 260 265 — 563 — — 1,088 Total allowance $ 15,603 $ 33,725 $ 13,049 $ 4,326 $ 374 $ 926 $ 68,003 Financing Receivables Individually evaluated for impairment $ 32,653 $ 159,497 $ 22,883 $ 6,632 $ 209 $ — $ 221,874 Collectively evaluated for impairment 4,395,621 1,758,897 1,492,803 765,417 43,616 46,163 8,502,517 ASC 310-30 loans 27,296 2,827 403 35,038 500 — 66,064 Loans Outstanding $ 4,455,570 $ 1,921,221 $ 1,516,089 $ 807,087 $ 44,325 $ 46,163 $ 8,790,455 As of September 30, 2018 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Allowance for loan and lease losses Individually evaluated for impairment $ 3,668 $ 9,590 $ 4,508 $ 2,210 $ 61 $ — $ 20,037 Collectively evaluated for impairment 12,430 18,266 9,102 2,277 196 1,026 43,297 ASC 310-30 loans 679 265 — 262 — — 1,206 Total allowance $ 16,777 $ 28,121 $ 13,610 $ 4,749 $ 257 $ 1,026 $ 64,540 Financing Receivables Individually evaluated for impairment $ 40,900 $ 137,225 $ 23,082 $ 6,686 $ 161 $ — $ 208,054 Collectively evaluated for impairment 4,053,712 1,823,947 1,364,511 780,047 48,711 46,487 8,117,415 ASC 310-30 loans 27,001 2,815 416 40,025 588 — 70,845 Loans Outstanding $ 4,121,613 $ 1,963,987 $ 1,388,009 $ 826,758 $ 49,460 $ 46,487 $ 8,396,314 For acquired loans not accounted for under ASC 310-30 (purchased non-impaired), the Company utilizes specific and collective reserve calculation methods similar to originated loans. The required ALLL for these loans is included in the individually evaluated for impairment bucket of the ALLL if the loan is rated substandard or worse, and in the collectively evaluated for impairment bucket for pass rated loans. The Company maintains an ALLL for acquired loans accounted for under ASC 310-30 as a result of impairment to loan pools arising from the periodic re-valuation of these loans. Any impairment in the individual pool is generally recognized in the current period as provision for loan and lease losses. Any improvement in the estimated cash flows, is generally not recognized immediately, but is instead reflected as an adjustment to the related loan pools yield on a prospective basis once any previously recorded impairment has been recaptured. The ALLL for ASC 310-30 loans totaled $1.1 million at March 31, 2019 , compared to $1.2 million at September 30, 2018 . For the three and six months ended March 31, 2019 , loan pools accounted for under ASC 310-30 had a net impairment of $0.3 million and a net reversal of provision of $0.1 million , respectively. For the three and six months ended March 31, 2018 , loan pools accounted for under ASC 310-30 had a net reversal of provision of $0.1 million and $0.1 million , respectively. The net impairment of provision for the three months ended March 31, 2019 due to actual cash flows being lower than expected while the net reversal of provision for the six months ended March 31, 2019 was a result of accretion resuming on an individually accounted for loan previously on cost recovery. The net reversal s of provision for the three and six months ended March 31, 2018 were driven by increases in expected cash flows. The reserve for unfunded loan commitments was $0.5 million at both March 31, 2019 and September 30, 2018 and is recorded in accrued expenses and other liabilities on the consolidated balance sheets.

Accounting for Certain Loans Ac

Accounting for Certain Loans Acquired with Deteriorated Credit Quality	6 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Accounting for Certain Loans Acquired with Deteriorated Credit Quality	Accounting for Certain Loans Acquired with Deteriorated Credit Quality In June 2010 and May 2016 , the Company acquired certain loans in the TierOne Bank and HF Financial transactions, respectively, that had deteriorated credit quality known as ASC 310-30 loans or purchased credit impaired loans. Several factors were considered when evaluating whether a loan was considered a purchased credit impaired loan, including the delinquency status of the loan, updated borrower credit status, geographic information and updated loan-to-values ("LTV"). Further, these purchased credit impaired loans had differences between contractual amounts owed and cash flows expected to be collected, that were at least in part, due to credit quality. U.S. GAAP allows purchasers to aggregate purchased credit impaired loans acquired in the same fiscal quarter in one or more pools, provided that the loans have common risk characteristics. A pool is then accounted for as a single asset with a single composite interest rate and an aggregate expectation of cash flows. Loan pools are periodically reassessed to determine expected cash flows. In determining the expected cash flows, the timing of cash flows and prepayment assumptions for smaller, homogeneous loans are based on statistical models that take into account factors such as the loan interest rate, credit profile of the borrowers, the years in which the loans were originated, and whether the loans are fixed or variable rate loans. Prepayments may be assumed on large individual loans that consider similar prepayment factors listed above for smaller homogeneous loans. The re-assessment of purchased credit impaired loans resulted in the following changes in the accretable yield during the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Balance at beginning of period $ 35,493 $ 41,918 $ 34,973 $ 44,131 Accretion (2,188 ) (3,664 ) (4,343 ) (7,045 ) Reclassification from (to) nonaccretable difference 375 (413 ) 3,050 755 Balance at end of period $ 33,680 $ 37,841 $ 33,680 $ 37,841 The reclassifications from nonaccretable difference noted in the table above represent instances where specific pools of loans are expected to perform better over the remaining lives of the loans than expected at the prior re-assessment date. The following table provides purchased credit impaired loans at March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Outstanding Balance ¹ Recorded Investment ² Carrying Value ³ Outstanding Balance ¹ Recorded Investment ² Carrying Value ³ (dollars in thousands) Commercial real estate $ 99,468 $ 27,296 $ 27,036 $ 100,761 $ 27,001 $ 26,322 Agriculture 4,622 2,827 2,562 4,841 2,815 2,551 Commercial non-real estate 7,419 403 403 7,475 416 416 Residential real estate 40,969 35,038 34,475 46,646 40,025 39,763 Consumer 555 500 500 656 588 588 Total lending $ 153,033 $ 66,064 $ 64,976 $ 160,379 $ 70,845 $ 69,640 1 Represents the legal balance of ASC 310-30 loans. 2 Represents the book balance of ASC 310-30 loans. 3 Represents the book balance of ASC 310-30 loans net of the related allowance for loan and lease losses.

FDIC Indemnification Asset

FDIC Indemnification Asset	6 Months Ended
	Mar. 31, 2019
Banking and Thrift [Abstract]
FDIC Indemnification Asset	FDIC Indemnification Asset Under the terms of the purchase and assumption agreement with the FDIC with regard to the TierOne Bank acquisition, the Company is reimbursed for a portion of the losses incurred on covered assets under the non-commercial loss share agreement. As covered assets are resolved, whether through repayment, short sale of the underlying collateral, the foreclosure on or sale of collateral, or the sale or charge-off of loans or other repossessed property, any differences between the carrying value of the covered assets versus the payments received during the resolution process that are reimbursable by the FDIC are recognized as reductions in the FDIC indemnification asset. Any gains or losses realized from the resolution of covered assets reduce or increase, respectively, the amount recoverable from the FDIC. The following table represents a summary of the activity related to the FDIC indemnification asset for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Balance at beginning of period $ 1,950 $ 4,692 $ 2,502 $ 5,704 Amortization (360 ) (732 ) (853 ) (1,750 ) Changes in expected reimbursements from FDIC for changes in expected credit losses (13 ) (15 ) (13 ) (33 ) Changes in reimbursable expenses (16 ) (456 ) (41 ) (662 ) (Reimbursements) payments of covered losses (from) to the FDIC (9 ) 189 (43 ) 419 Balance at end of period $ 1,552 $ 3,678 $ 1,552 $ 3,678 The loss claims filed are subject to review, approval, and annual audits by the FDIC or its assigned agents for compliance with the terms in the loss sharing agreement which ends June 4, 2020 .

Derivative Financial Instrument

Derivative Financial Instruments	6 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The Company uses interest rate swaps to manage its interest rate risk and market risk in accommodating the needs of its customers. 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 March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Notional Amount Gross Asset Gross Liability Notional Amount Gross Asset Gross Liability (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps Financial institution counterparties $ 1,237,398 $ 4,394 $ (12,824 ) $ 1,082,630 $ 22,696 $ (2,231 ) Customer counterparties 430,434 20,676 (40 ) 217,066 1,533 (2,160 ) Mortgage loan commitments 22,463 21 — 22,195 — (28 ) Mortgage loan forward sale contracts 25,103 — (21 ) 27,408 28 — Total $ 1,715,398 $ 25,091 $ (12,885 ) $ 1,349,299 $ 24,257 $ (4,419 ) 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 March 31, 2019 and September 30, 2018 . Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of March 31, 2019 Total Derivative Assets $ 25,091 $ (3,198 ) $ 3,950 $ 25,843 Total Derivative Liabilities ¹ $ (12,885 ) $ 3,198 $ 9,629 $ (58 ) 1 There was an additional $11.4 million of collateral held for initial margin with our Futures Clearing Merchant for clearing derivatives at March 31, 2019 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, 2018 Total Derivative Assets $ 24,257 $ (2,231 ) $ (20,115 ) $ 1,911 Total Derivative Liabilities ¹ (4,419 ) 2,231 — (2,188 ) 1 There was an additional $6.2 million of collateral held for initial margin with our Futures Clearing Merchant for clearing derivatives at September 30, 2018 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. Beginning in the second quarter of fiscal year 2018, the Company entered 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 notional amounts of RPAs sold were $49.7 million and $37.4 million as of March 31, 2019 and September 30, 2018 , respectively. Assuming all underlying loan customers defaulted on their obligation to perform under the interest rate swap with a derivative counterparty, the exposure from these RPAs would be $4.9 million and $0.4 million at March 31, 2019 and September 30, 2018 , respectively, based on the fair value of the underlying swaps. The effect of derivatives on the consolidated statements of income for the three and six months ended March 31, 2019 and 2018 was as follows. Amount of (Loss) Gain Recognized in Consolidated Statements of Income Three Months Ended March 31, Six Months Ended March 31, Location of (Loss) Gain Recognized in Consolidated Statements of Income 2019 2018 2019 2018 (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps Net realized and unrealized (loss) gain on derivatives $ (11,032 ) $ 14,282 $ (29,348 ) $ 21,509 Mortgage loan commitments Net realized and unrealized (loss) gain on derivatives 9 2 21 3 Mortgage loan forward sale contracts Net realized and unrealized (loss) gain on derivatives (9 ) (2 ) (21 ) (3 )

The Fair Value Option for Certa

The Fair Value Option for Certain Loans	6 Months Ended
	Mar. 31, 2019
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 16 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 unfavorable difference between the aggregate fair value and the aggregate unpaid loan principal balance and written loan commitment amount of approximately $0.5 million at March 31, 2019 and a net unfavorable difference of approximately $34.8 million at September 30, 2018 . The total unpaid principal balance of these long-term loans was approximately $836.3 million and $900.2 million at March 31, 2019 and September 30, 2018 , 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 March 31, 2019 and September 30, 2018 , there were loans with a fair value of $20.7 million and $30.9 million , respectively, which were greater than 90 days past due or in nonaccrual status with an unpaid principal balance of $24.5 million and $34.7 million , respectively. Changes in fair value for items for which the fair value option has been elected and the line items in which these changes are reported within the consolidated statements of income are as follows for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Noninterest Income (Loss) Total Changes in Fair Value Noninterest Income (Loss) Total Changes in Fair Value Noninterest Income (Loss) Total Changes in Fair Value Noninterest Income (Loss) Total Changes in Fair Value (dollars in thousands) Long-term loans $ 14,018 $ 14,018 $ (14,838 ) $ (14,838 ) $ 33,234 $ 33,234 $ (23,502 ) $ (23,502 ) For long-term loans, $0.4 million and $1.4 million for the three months ended March 31, 2019 and 2018 and $0.8 million and $0.3 million for the six months ended March 31, 2019 and 2018 , 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	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and September 30, 2018 . Core Deposit Intangible Brand Other Total (dollars in thousands) As of March 31, 2019 Gross carrying amount $ 7,339 $ 8,464 $ 538 $ 16,341 Accumulated amortization (3,083 ) (6,110 ) (224 ) (9,417 ) Net intangible assets $ 4,256 $ 2,354 $ 314 $ 6,924 As of September 30, 2018 Gross carrying amount $ 7,339 $ 8,464 $ 538 $ 16,341 Accumulated amortization (2,610 ) (5,828 ) (191 ) (8,629 ) Net intangible assets $ 4,729 $ 2,636 $ 347 $ 7,712 Amortization expense of intangible assets was $0.4 million for both the three months ended March 31, 2019 and 2018 and $0.8 million and $0.9 million for the six months ended March 31, 2019 and 2018 , 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 2019 $ 750 2020 1,430 2021 1,334 2022 1,249 2023 967 2024 and thereafter 1,194 Total $ 6,924

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase	6 Months Ended
	Mar. 31, 2019
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 $101.2 million and $109.9 million and fair value of approximately $98.8 million and $104.6 million at March 31, 2019 and September 30, 2018 , respectively. In most cases, in alignment with the repurchase agreements in place with our 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 March 31, 2019 and September 30, 2018 . March 31, 2019 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 62,537 — — — 62,537 Total repurchase agreements $ 62,537 $ — $ — $ — $ 62,537 September 30, 2018 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 90,907 — — — 90,907 Total repurchase agreements $ 90,907 $ — $ — $ — $ 90,907

FHLB Advances and Other Borrowi

FHLB Advances and Other Borrowings	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and September 30, 2018 . March 31, September 30, 2019 2018 (dollars in thousands) Short-term borrowings: FHLB fed funds advance, matured $ — $ 100,000 Long-term borrowings: Notes payable to FHLB, interest rates from 2.68% to 3.66% and maturity dates from March 2021 to September 2024, collateralized by real estate loans, with various call dates at the option of the FHLB 275,000 175,000 Total $ 275,000 $ 275,000 As of March 31, 2019 and September 30, 2018 , the Company had a borrowing capacity of $1.64 billion and $1.59 billion , respectively, with the FRB Discount Window. Principal balances of loans pledged to FRB Discount Window to collateralize the borrowing totaled $1.94 billion at March 31, 2019 and $1.89 billion at September 30, 2018 . The Company has secured this line for contingency funding. As of March 31, 2019 and September 30, 2018 , based on its collateral pledged, the additional borrowing capacity of the Company with the FHLB was $2.04 billion and $1.82 billion , respectively. Principal balances of loans pledged to the FHLB to collateralize notes payable totaled $4.48 billion and $3.95 billion at March 31, 2019 and September 30, 2018 , respectively. The Company purchased letters of credit from the FHLB to pledge as collateral on public deposits. The amount outstanding was $217.0 million and $150.0 million at March 31, 2019 and September 30, 2018 , respectively. As of March 31, 2019 , 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 2019 $ — 2020 — 2021 70,000 2022 60,000 2023 85,000 2024 and thereafter 60,000 Total $ 275,000

Subordinated Debentures and Sub

Subordinated Debentures and Subordinated Notes Payable	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 have issued and outstanding in the aggregate 73,400 shares, $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 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 March 31, 2019 and September 30, 2018 , $73.6 million of Debentures, net of fair value adjustment, were eligible for treatment as Tier 1 capital. Relating to the trusts, the Company held as assets $2.5 million in common shares at March 31, 2019 and September 30, 2018 , 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, which qualify as Tier 2 capital under Capital Rules in effect at March 31, 2019 , have an interest rate of 4.875% per annum, payable semi-annually on each February 15 and August 15 , which commenced on February 15, 2016 until August 15, 2020 , or the date of earlier redemption, and then from August 15, 2020 to the stated maturity date or earlier redemption, the notes will 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 in the event of bankruptcy or the occurrence of certain other events of bankruptcy, insolvency or reorganization. Unamortized debt issuance costs related to these notes, which are included in Subordinated Debentures and Subordinated Notes Payable, totaled $0.1 million at March 31, 2019 and September 30, 2018 . Proceeds from the private placement of subordinated notes repaid outstanding subordinated debt. Subordinated debentures and subordinated notes payable are summarized as follows. March 31, 2019 September 30, 2018 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 (2,294 ) (2,317 ) Total junior subordinated debentures payable, net of fair value adjustment 73,626 73,603 Subordinated notes payable Fixed to floating rate, 4.875% per annum 35,000 35,000 Less: unamortized debt issuance costs (98 ) (135 ) Total subordinated notes payable 34,902 34,865 Total subordinated debentures and subordinated notes payable $ 108,528 $ 108,468 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	6 Months Ended
	Mar. 31, 2019
Retirement Benefits [Abstract]
Profit Sharing Plan	Profit Sharing Plan The 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 $1.1 million and $1.2 million to the 401(k) Plan for the three months ended March 31, 2019 and 2018 and $2.9 million and $3.0 million for the six months ended March 31, 2019 and 2018 , respectively.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [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 our 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, our 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 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 both of the three months ended March 31, 2019 and 2018 and $3.1 million and $2.9 million for the six months ended March 31, 2019 and 2018 , respectively. Related income tax benefits recognized were $0.4 million for both of the three months ended March 31, 2019 and 2018 and $0.8 million and $1.0 million for the six months ended March 31, 2019 and 2018 , respectively. The following is a summary of the Plans’ restricted share and performance-based stock award activity as of March 31, 2019 and September 30, 2018 . The number of performance shares granted in the following table are reflected at the amount of achievement of the pre-established targets. March 31, 2019 September 30, 2018 Common Weighted-Average Grant Date Fair Value Common Weighted-Average Grant Date Fair Value Restricted Shares Restricted shares, beginning of fiscal year 163,287 $ 37.86 180,337 $ 33.06 Granted 106,364 37.29 89,376 41.07 Vested (74,242 ) 38.65 (97,682 ) 32.11 Forfeited (641 ) 39.53 (8,744 ) 35.99 Canceled — — — — Restricted shares, end of period 194,768 $ 37.24 163,287 $ 37.86 Vested, but not issuable at end of period 50,770 $ 33.88 39,514 $ 32.90 Performance Shares Performance shares, beginning of fiscal year 175,196 $ 36.29 133,604 $ 33.39 Granted 70,107 28.55 53,682 29.52 Vested (59,803 ) 30.78 (7,017 ) 18.00 Forfeited (93 ) 37.72 (5,073 ) 37.75 Canceled — — — — Performance shares, end of period 185,407 $ 38.50 175,196 $ 36.29 Vested, but not issuable at end of period 5,612 $ 18.00 5,612 $ 18.00 As of March 31, 2019 , there was $8.3 million of unrecognized compensation cost related to non-vested restricted stock awards expected to be recognized over a period of 2.7 years . The fair value of the vested, but not issued stock awards was $1.8 million and $1.9 million at March 31, 2019 and September 30, 2018 , respectively.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Mar. 31, 2019
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 three levels of inputs that may be used to measure fair value are as follows. 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 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 March 31, 2019 and September 30, 2018 . 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 our 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 March 31, 2019 and September 30, 2018 . Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of March 31, 2019 U.S. Treasury securities $ 93,819 $ 93,819 $ — $ — Mortgage-backed securities 1,605,616 — 1,605,616 — States and political subdivision securities 62,870 — 61,559 1,311 Other 1,000 — 1,000 — Total securities available for sale $ 1,763,305 $ 93,819 $ 1,668,175 $ 1,311 Derivatives-assets $ 25,843 $ — $ 25,843 $ — Derivatives-liabilities 58 — 58 — Fair value loans 835,822 — 835,822 — Loan servicing rights 2,674 — — 2,674 As of September 30, 2018 U.S. Treasury securities $ 167,172 $ 167,172 $ — $ — Mortgage-backed securities 1,149,707 — 1,149,707 — States and political subdivision securities 67,775 — 66,805 970 Other 996 — 996 — Total securities available for sale $ 1,385,650 $ 167,172 $ 1,217,508 $ 970 Derivatives-assets $ 1,911 $ — $ 1,911 $ — Derivatives-liabilities 2,188 — 2,188 — Fair value loans 865,386 — 865,386 — Loan servicing rights 3,087 — — 3,087 The following table presents the changes in Level 3 assets and liabilities measured at fair value on a recurring basis for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Other securities available for sale Balance, beginning of period $ 961 $ 965 $ 970 $ 1,069 Additions 350 — 350 — Principal paydown — — (9 ) (104 ) Balance, end of period $ 1,311 $ 965 $ 1,311 $ 965 Loan servicing rights Balance, beginning of period $ 2,862 $ 3,799 $ 3,087 $ 4,074 Realized and unrealized loss ¹ (188 ) (213 ) (413 ) (488 ) Balance, end of period $ 2,674 $ 3,586 $ 2,674 $ 3,586 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 tables present 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 March 31, 2019 and September 30, 2018 . Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of March 31, 2019 Other repossessed property $ 31,834 $ — $ — $ 31,834 Impaired loans 200,312 — — 200,312 Loans held for sale, at lower of cost or fair value 3,648 — 3,648 — Property held for sale 3,216 — — 3,216 As of September 30, 2018 Other repossessed property $ 22,225 $ — $ — $ 22,225 Impaired loans 188,017 — — 188,017 Loans held for sale, at lower of cost or fair value 5,456 — 5,456 — Property held for sale 1,104 — — 1,104 The valuation techniques and significant unobservable inputs used to measure Level 3 fair value measurements at March 31, 2019 were as follows. Fair Value of Assets / (Liabilities) at March 31, 2019 Valuation Unobservable Range Weighted (dollars in thousands) Other repossessed property $ 31,834 Appraisal value Property specific adjustment N/A N/A Impaired loans 200,312 Appraisal value Property specific adjustment N/A N/A Property held for sale 3,216 Appraisal value Property specific adjustment N/A N/A Disclosures about Fair Value of Financial Instruments The following section summarizes the estimated fair value for financial instruments accounted for at amortized cost as of as of March 31, 2019 and September 30, 2018 . Significant assets and liabilities that are not considered financial instruments 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 March 31, 2019 and September 30, 2018 are as follows. March 31, 2019 September 30, 2018 Level in Fair Value Hierarchy Carrying Amount Fair Carrying Amount Fair (dollars in thousands) Assets Cash and cash equivalents Level 1 $ 282,638 $ 282,638 $ 298,696 $ 298,696 Loans, net, excluding fair valued loans, loans held for sale and impaired loans ¹ Level 3 8,731,128 8,721,910 8,357,065 8,231,829 Liabilities Time deposits Level 2 2,087,558 2,086,538 1,847,078 1,848,550 FHLB advances and other borrowings Level 2 275,000 280,374 275,000 275,797 Securities sold under repurchase agreements Level 2 62,537 62,537 90,907 90,907 Subordinated debentures and subordinated notes payable Level 2 108,528 102,285 108,468 107,841 1 Includes $13.5 million and $13.0 million of net deferred loan fees at March 31, 2019 and September 30, 2018, respectively, of which carrying value approximates fair value.

Earnings per Share

Earnings per Share	6 Months Ended
	Mar. 31, 2019
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 and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands, except per share data) Net income $ 44,511 $ 40,532 $ 90,297 $ 69,762 Weighted average common shares outstanding 56,994,817 58,941,315 57,484,838 58,921,972 Dilutive effect of stock based compensation 79,857 204,802 72,146 194,951 Weighted average common shares outstanding for diluted earnings per share calculation 57,074,674 59,146,117 57,556,984 59,116,923 Basic earnings per share $ 0.78 $ 0.69 $ 1.57 $ 1.18 Diluted earnings per share $ 0.78 $ 0.69 $ 1.57 $ 1.18 The Company had no shares of unvested performance stock as of March 31, 2019 and 2018 , 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 67,971 and no shares of anti-dilutive stock awards outstanding as of March 31, 2019 and 2018 , respectively.

Nature of Operations and Summ_2

Nature of Operations and Summary of Significant Policies (Policies)	6 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated interim financial statements have been prepared in accordance with U.S. 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, 2018 , 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 U.S. 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.
Revenue Recognition	Revenue Recognition We adopted ASU 2014-09, " Revenue from Contracts with Customers (Topic 606) " and subsequent related ASUs effective October 1, 2018 using the modified retrospective approach, which establishes principles for reporting information about the nature, amount, timing and uncertainty of revenue and cash flows arising from the Company's contracts to provide goods or services to 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 our revenue-generating transactions are not subject to ASC Topic 606, including revenue generated from financial instruments, such as our loans, letters of credit, derivatives and investment securities, as well as revenue related to our mortgage servicing activities, as these activities are subject to other GAAP discussed elsewhere within our disclosures and in "Note 1. Nature of Operations and Summary of Significant Policies ," in the Company's Annual Report on Form 10-K for the fiscal year ended September 30, 2018 . Descriptions of our revenue-generating activities that are within the scope of ASC Topic 606, which are presented in our 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 March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Noninterest income Service charges and other fees $ 10,209 $ 12,047 $ 21,897 $ 25,224 Wealth management fees 2,117 2,335 4,358 4,519 Other 1,118 3,351 1,700 4,002 Noninterest income from contracts with customers within the scope of ASC Topic 606 ¹ 13,444 17,733 27,955 33,745 Noninterest income within the scope of other GAAP Topics ² 4,779 1,009 6,988 1,671 Total noninterest income $ 18,223 $ 18,742 $ 34,943 $ 35,416 1 Amounts for periods after October 1, 2018 are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers , except for out of scope amounts. Amounts for periods prior to October 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition , and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers . 2 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. At March 31, 2019 , the Company does not have any material contract assets, liabilities, or other receivables recorded on its consolidated balance sheets relating to its revenue streams within the scope of ASC Topic 606. Additionally, the Company's contracts generally do not contain terms that require significant judgment to determine the amount of revenue to recognize. Practical expedients The Company has elected the practical expedient to exclude the disclosure of unsatisfied performance obligations for contracts with an original expected length of one year or less and (ii) contracts for which the Company recognizes revenue at the amount to which the Company has the right to invoice for services performed. The Company recognizes incremental costs of obtaining those contracts as an expense when incurred.
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 other 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 Pronouncements	Accounting Standards Adopted in Fiscal Year 2019 In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , which implements a more robust framework that clarifies the principles for recognizing revenue and gives greater consistency and comparability in revenue recognition practices. In the new framework, an entity recognizes revenue in an amount that reflects the consideration to which the entity expects to be entitled in exchange for goods or services. The new model requires the identification of performance obligations included in the contract with customers, a determination of the transaction price and an allocation of the price to those performance obligations. The entity recognizes revenue when performance obligations are satisfied. In August 2015, the FASB issued ASU 2015-14, which deferred the effective date of ASU 2014-09 to annual reporting periods beginning after December 15, 2017. In March 2016, the FASB issued ASU 2016-08, which clarifies the implementation guidance on principal versus agent considerations. In April 2016, the FASB issued ASU 2016-10, which clarifies guidance pertaining to the identification of performance obligations and the licensing implementation. In May 2016, the FASB issued ASU 2016-11 and 2016-12, which further clarify guidance and provide practical expedients related to the adoption of ASU 2014-09. In December 2016, the FASB issued ASU 2016-20, which made technical corrections and improvements to the previous ASUs issued. The standard permits the use of either the retrospective or cumulative effect transition method. The standard, along with subsequent guidance from FASB, lists several items that are specifically out of scope for ASU 2014-09, including but not limited to core interest income, derivative instruments, investments, and loan origination fees. The Company adopted this standard and subsequent related ASUs October 1, 2018 using the modified retrospective method. Furthermore, the Company prospectively changed the presentation of direct expenses, including reward costs, associated with credit and debit card interchange income previously included in data processing and communication expense which are now netted against interchange income in service charges and other fees, which is included in noninterest income on the consolidated statements of income. Brokerage charges previously included in professional fees are now netted against wealth management fees, which is included in noninterest income on the consolidated statements of income. The net quantitative impact of these presentation changes decreased both revenue and expenses by $2.0 million and $3.7 million for the three and six months ended March 31, 2019 ; however, these presentation changes did not have an impact on net income. Prior period balances have not been restated to reflect these presentation changes. There were no significant cumulative effect adjustments as a result of implementation as our current revenue recognition policies generally conform with the principals in ASC Topic 606. For additional information, see "Note 1. Nature of Operations and Summary of Significant Policies ." Accounting Standards Not Yet Adopted in Fiscal Year 2019 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 our consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities , which amends the hedge accounting recognition and presentation requirements in ASC 815 to improve the transparency and understandability of information conveyed to financial statement users about an entity’s risk management activities to better align the entity’s financial reporting for hedging relationships with those risk management activities and to reduce the complexity of and simplify the application of hedge accounting. ASU 2017-12 is to be applied to all existing hedging relationships on the date of adoption and will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted in any interim period, with the effect of adoption reflected as of the beginning of the fiscal year of adoption. The Company is currently evaluating the potential impact of ASU 2017-12 on our consolidated financial statements and does not expect to early adopt this standard. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which addresses timelier recording of credit losses on loans and other financial instruments held by financial institutions and other organizations. ASU 2016-13 requires institutions to measure all expected credit losses related to financial assets measured at amortized costs 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 current expected credit loss (CECL) model. ASU 2016-13 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. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments, Credit Losses , which made technical corrections and improvements to the previous ASU issued. These ASUs will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with early adoption permitted after December 15, 2018. The amendment requires the use of the modified retrospective approach for adoption. The Company continues to make progress on the implementation plan and has submitted historical data to third party vendor to start making necessary changes to our existing credit loss estimation process. The Company does not expect to early adopt this standard and is currently evaluating the potential impact on our consolidated financial statements; however, since the magnitude of the anticipated change in the allowance for credit losses will be impacted by economic conditions and trends in the Company’s portfolio at the time of adoption, the quantitative impact cannot yet be reasonably estimated. In February 2016, the FASB issued ASU 2016-02 , Leases (Topic 842) , which requires that lessees recognize the assets and liabilities arising from leases on the balance sheet and disclosing key information about leasing arrangements. Lessees will be required to recognize an obligation for future lease payments measured on a discounted basis and a related right-of-use asset. ASU 2016-02 does not significantly change lease accounting requirements applicable to lessors; however, certain changes were made to align, where necessary, lessor accounting with the lessee accounting model and ASC Topic 606, Revenue from Contracts with Customers . In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases , and ASU 2018-11, Leases (Topic 842), Targeted Improvements , which made technical corrections and improvements to the previous ASU issued. In December 2018, the FASB issued ASU 2018-20, Leases (Topic 842): Narrow-Scope Improvements for Lessors , which allows lessors to exclude sales tax from consideration of the contract through a policy election and clarifies treatment of certain lessor costs and variable payments for contracts with lease and nonlease components. These ASUs will be effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The guidance will be effective with respect to the Company beginning fiscal year 2020. The Company has a project team working on the implementation plan, is currently reviewing all existing lease agreements for which the amended guidance is to be applied, is in the process of determining which practical expedients will be elected for transition and is currently evaluating the potential impact on our consolidated financial statements.

Nature of Operations and Summ_3

Nature of Operations and Summary of Significant Policies (Tables)	6 Months Ended
	Mar. 31, 2019
Accounting Policies [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 March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Noninterest income Service charges and other fees $ 10,209 $ 12,047 $ 21,897 $ 25,224 Wealth management fees 2,117 2,335 4,358 4,519 Other 1,118 3,351 1,700 4,002 Noninterest income from contracts with customers within the scope of ASC Topic 606 ¹ 13,444 17,733 27,955 33,745 Noninterest income within the scope of other GAAP Topics ² 4,779 1,009 6,988 1,671 Total noninterest income $ 18,223 $ 18,742 $ 34,943 $ 35,416 1 Amounts for periods after October 1, 2018 are presented in accordance with ASC Topic 606, Revenue from Contracts with Customers , except for out of scope amounts. Amounts for periods prior to October 1, 2018 are presented in accordance with ASC Topic 605, Revenue Recognition , and have not been restated to conform with ASC Topic 606, Revenue from Contracts with Customers . 2 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.

Securities Available for Sale (

Securities Available for Sale (Tables)	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 U.S. Treasury securities $ 93,696 $ 419 $ (296 ) $ 93,819 Mortgage-backed securities: Government National Mortgage Association 491,888 1,811 (9,909 ) 483,790 Federal Home Loan Mortgage Corporation 438,605 3,697 (2,839 ) 439,463 Federal National Mortgage Association 303,643 1,268 (2,386 ) 302,525 Small Business Assistance Program 382,165 514 (2,841 ) 379,838 States and political subdivision securities 63,400 151 (681 ) 62,870 Other 1,006 — (6 ) 1,000 Total $ 1,774,403 $ 7,860 $ (18,958 ) $ 1,763,305 Amortized Gross Unrealized Gains Gross Unrealized Losses Estimated (dollars in thousands) As of September 30, 2018 U.S. Treasury securities $ 168,394 $ — $ (1,222 ) $ 167,172 Mortgage-backed securities: Government National Mortgage Association 442,458 35 (16,335 ) 426,158 Federal Home Loan Mortgage Corporation 297,380 — (7,055 ) 290,325 Federal National Mortgage Association 188,192 — (6,081 ) 182,111 Small Business Assistance Program 260,458 — (9,345 ) 251,113 States and political subdivision securities 69,566 4 (1,795 ) 67,775 Other 1,006 — (10 ) 996 Total $ 1,427,454 $ 39 $ (41,843 ) $ 1,385,650 The amortized cost and approximate fair value of debt securities available for sale as of March 31, 2019 and September 30, 2018 , 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. March 31, 2019 September 30, 2018 Amortized Estimated Amortized Estimated (dollars in thousands) Due in one year or less $ 36,309 $ 36,153 $ 111,842 $ 111,221 Due after one year through five years 111,862 111,756 114,920 113,069 Due after five years through ten years 8,803 8,658 11,076 10,535 Due after ten years 122 122 122 122 157,096 156,689 237,960 234,947 Mortgage-backed securities 1,616,301 1,605,616 1,188,488 1,149,707 Securities without contractual maturities 1,006 1,000 1,006 996 Total $ 1,774,403 $ 1,763,305 $ 1,427,454 $ 1,385,650
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 March 31, 2019 U.S. Treasury securities $ — $ — $ 44,232 $ (296 ) $ 44,232 $ (296 ) Mortgage-backed securities 126,015 (468 ) 865,274 (17,507 ) 991,289 (17,975 ) States and political subdivision securities — — 49,649 (681 ) 49,649 (681 ) Other — — 1,000 (6 ) 1,000 (6 ) Total $ 126,015 $ (468 ) $ 960,155 $ (18,490 ) $ 1,086,170 $ (18,958 ) Less than 12 months 12 months or more Total Estimated Unrealized Estimated Unrealized Estimated Unrealized (dollars in thousands) As of September 30, 2018 U.S. Treasury securities $ 167,172 $ (1,222 ) $ — $ — $ 167,172 $ (1,222 ) Mortgage-backed securities 416,677 (8,427 ) 709,387 (30,389 ) 1,126,064 (38,816 ) States and political subdivision securities 23,534 (250 ) 42,282 (1,545 ) 65,816 (1,795 ) Other 996 (10 ) — — 996 (10 ) Total $ 608,379 $ (9,909 ) $ 751,669 $ (31,934 ) $ 1,360,048 $ (41,843 )

Loans (Tables)

Loans (Tables)	6 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Schedule of loans receivable	The following table presents the composition of loans as of March 31, 2019 and September 30, 2018 . March 31, September 30, 2019 2018 (dollars in thousands) Commercial real estate $ 5,049,792 $ 4,629,330 Agriculture 2,121,872 2,182,688 Commercial non-real estate 1,721,095 1,699,987 Residential real estate 815,212 837,569 Consumer 44,504 49,689 Other 46,163 46,487 Ending balance 9,798,638 9,445,750 Less: Unamortized discount on acquired loans (15,255 ) (18,283 ) Unearned net deferred fees and costs and loans in process (12,472 ) (11,543 ) Total $ 9,770,911 $ 9,415,924
Schedule of the Company's nonaccrual loans	The following table presents the Company’s nonaccrual loans at March 31, 2019 and September 30, 2018 , excluding ASC 310-30 loans. Loans greater than 90 days past due and still accruing interest as of March 31, 2019 and September 30, 2018 , were $0.0 million and $0.2 million , respectively. March 31, September 30, 2019 2018 (dollars in thousands) Nonaccrual loans Commercial real estate $ 17,929 $ 22,871 Agriculture 91,771 107,198 Commercial non-real estate 6,868 6,887 Residential real estate 2,499 3,549 Consumer 87 61 Total $ 119,154 $ 140,566
Schedule of the composition of the loan portfolio by internal risk rating	This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . As of March 31, 2019 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer ¹ Other Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,455,347 $ 1,584,602 $ 1,512,883 $ 762,495 $ 44,013 $ 46,163 $ 8,405,503 Watchlist 47,424 199,585 32,402 5,450 102 — 284,963 Substandard 32,938 158,061 20,926 6,435 210 — 218,570 Doubtful 61 137 1,325 29 — — 1,552 Loss — — — — — — — Ending balance 4,535,770 1,942,385 1,567,536 774,409 44,325 46,163 8,910,588 Loans covered by a FDIC loss sharing agreement — — — 36,975 — — 36,975 Total $ 4,535,770 $ 1,942,385 $ 1,567,536 $ 811,384 $ 44,325 $ 46,163 $ 8,947,563 1 The Company generally does not risk rate residential real estate or consumer 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 loans. As of September 30, 2018 Commercial Real Estate Agriculture Commercial Residential Real Estate ¹ Consumer ¹ Other Total (dollars in thousands) Credit Risk Profile by Internally Assigned Grade Grade: Pass $ 4,108,314 $ 1,610,291 $ 1,401,418 $ 779,610 $ 48,979 $ 46,487 $ 7,995,099 Watchlist 53,150 239,392 19,503 4,548 322 — 316,915 Substandard 41,184 137,205 20,117 6,366 159 — 205,031 Doubtful 93 2 2,277 37 — — 2,409 Loss — — — — — — — Ending balance 4,202,741 1,986,890 1,443,315 790,561 49,460 46,487 8,519,454 Loans covered by a FDIC loss sharing agreement — — — 42,627 — — 42,627 Total $ 4,202,741 $ 1,986,890 $ 1,443,315 $ 833,188 $ 49,460 $ 46,487 $ 8,562,081 1 The Company generally does not risk rate residential real estate or consumer 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 loans.
Schedule of past due loans	The following table presents the Company’s past due loans at March 31, 2019 and September 30, 2018 . This table is presented net of unamortized discount on acquired loans and excludes loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Current Total Financing Receivables (dollars in thousands) As of March 31, 2019 Commercial real estate $ 3,051 $ 95 $ 5,519 $ 8,665 $ 4,527,105 $ 4,535,770 Agriculture 11,558 8,985 37,075 57,618 1,884,767 1,942,385 Commercial non-real estate 2,161 4,134 3,452 9,747 1,557,789 1,567,536 Residential real estate 2,341 700 803 3,844 770,565 774,409 Consumer 208 15 — 223 44,102 44,325 Other — — — — 46,163 46,163 Ending balance 19,319 13,929 46,849 80,097 8,830,491 8,910,588 Loans covered by a FDIC loss sharing agreement 1,955 78 214 2,247 34,728 36,975 Total $ 21,274 $ 14,007 $ 47,063 $ 82,344 $ 8,865,219 $ 8,947,563 30-59 Days Past Due 60-89 Days Past Due 90 Days or Greater Past Due Total Current Total Financing Receivables (dollars in thousands) As of September 30, 2018 Commercial real estate $ 920 $ 551 $ 9,135 $ 10,606 $ 4,192,135 $ 4,202,741 Agriculture 1,243 2,042 51,579 54,864 1,932,026 1,986,890 Commercial non-real estate 551 16 4,068 4,635 1,438,680 1,443,315 Residential real estate 913 200 1,747 2,860 787,701 790,561 Consumer 83 47 1 131 49,329 49,460 Other — — — — 46,487 46,487 Ending balance 3,710 2,856 66,530 73,096 8,446,358 8,519,454 Loans covered by a FDIC loss sharing agreement 30 233 471 734 41,893 42,627 Total $ 3,740 $ 3,089 $ 67,001 $ 73,830 $ 8,488,251 $ 8,562,081
Schedule of impaired loans	The following table presents the Company’s impaired loans. This table excludes purchased credit impaired loans and loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . March 31, 2019 September 30, 2018 Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance (dollars in thousands) Impaired loans: With an allowance recorded: Commercial real estate $ 22,058 $ 22,102 $ 2,258 $ 25,136 $ 25,223 $ 3,668 Agriculture 67,476 81,601 14,281 60,053 76,874 9,590 Commercial non-real estate 14,214 16,933 3,338 14,177 17,241 4,508 Residential real estate 3,093 3,678 1,562 4,509 5,153 2,210 Consumer 209 213 123 160 165 61 Total impaired loans with an allowance recorded 107,050 124,527 21,562 104,035 124,656 20,037 With no allowance recorded: Commercial real estate 10,595 50,487 — 15,764 58,141 — Agriculture 92,021 102,968 — 77,172 80,355 — Commercial non-real estate 8,669 17,809 — 8,905 18,047 — Residential real estate 3,539 5,969 — 2,177 4,574 — Consumer — 117 — 1 118 — Total impaired loans with no allowance recorded 114,824 177,350 — 104,019 161,235 — Total impaired loans $ 221,874 $ 301,877 $ 21,562 $ 208,054 $ 285,891 $ 20,037 The following table presents the average recorded investment on impaired loans and interest income recognized on impaired loans for the three and six months ended March 31, 2019 and 2018 . Three Months Ended Six Months Ended March 31, 2019 March 31, 2018 March 31, 2019 March 31, 2018 Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status (dollars in thousands) Commercial real estate $ 34,475 $ 345 $ 66,577 $ 477 $ 36,616 $ 697 $ 56,875 $ 2,053 Agriculture 151,021 2,203 121,062 1,189 146,423 3,202 124,200 2,171 Commercial non-real estate 22,556 312 30,350 325 22,731 678 30,878 776 Residential real estate 6,724 93 7,578 116 6,711 182 7,636 281 Consumer 237 6 238 4 212 11 256 8 Total $ 215,013 $ 2,959 $ 225,805 $ 2,111 $ 212,693 $ 4,770 $ 219,845 $ 5,289 The following table provides purchased credit impaired loans at March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Outstanding Balance ¹ Recorded Investment ² Carrying Value ³ Outstanding Balance ¹ Recorded Investment ² Carrying Value ³ (dollars in thousands) Commercial real estate $ 99,468 $ 27,296 $ 27,036 $ 100,761 $ 27,001 $ 26,322 Agriculture 4,622 2,827 2,562 4,841 2,815 2,551 Commercial non-real estate 7,419 403 403 7,475 416 416 Residential real estate 40,969 35,038 34,475 46,646 40,025 39,763 Consumer 555 500 500 656 588 588 Total lending $ 153,033 $ 66,064 $ 64,976 $ 160,379 $ 70,845 $ 69,640 1 Represents the legal balance of ASC 310-30 loans. 2 Represents the book balance of ASC 310-30 loans. 3 Represents the book balance of ASC 310-30 loans net of the related allowance for loan and lease losses.
Summary of troubled debt restructurings on accruing and nonaccrual loans	The following table presents the recorded value of the Company’s TDR balances as of March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Accruing Nonaccrual Accruing Nonaccrual (dollars in thousands) Commercial real estate $ 1,930 $ 1,068 $ 2,649 $ 2,616 Agriculture 12,377 46,592 13,248 73,741 Commercial non-real estate 2,498 705 3,420 656 Residential real estate 347 115 389 143 Consumer 91 61 77 — Total $ 17,243 $ 48,541 $ 19,783 $ 77,156 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 and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Recorded Investment Recorded Investment Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Commercial real estate — $ — $ — — $ — $ — — $ — $ — — $ — $ — Agriculture — — — 2 6,073 6,073 — $ — — 2 6,073 6,073 Commercial non-real estate — — — — — — — $ — — — — — Residential real estate — — — — — — — — — — — — Consumer — — — 1 73 73 1 $ 89 89 1 73 73 Total accruing — $ — $ — 3 $ 6,146 $ 6,146 1 $ 89 $ 89 3 $ 6,146 $ 6,146 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — — — — — — — The following table presents a summary of all nonaccruing loans restructured in TDRs for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Recorded Investment Recorded Investment Recorded Investment Recorded Investment Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification Number Pre-Modification Post-Modification (dollars in thousands) Commercial real estate — $ — $ — — $ — $ — — $ — $ — — $ — $ — Agriculture — — — 6 8,374 8,374 — $ — — 6 8,374 8,374 Commercial non-real estate — — — — — — — $ — — — — — Residential real estate — — — — — — — — — — — — Consumer — — — — — — — $ — — — — — Total nonaccruing — $ — $ — 6 $ 8,374 $ 8,374 — $ — $ — 6 $ 8,374 $ 8,374 Change in recorded investment due to principal paydown at time of modification — $ — $ — — $ — $ — — $ — $ — — $ — $ — Change in recorded investment due to chargeoffs at time of modification — — — — — — — — — — — — The following table presents loans that were modified as TDRs within the previous 12 months and for which there was a payment default for the three and six months ended March 31, 2019 and 2018 , respectively. Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Loans Recorded Investment Number of Loans Recorded Investment (dollars in thousands) Commercial real estate — $ — — $ — — $ — 1 $ 1,012 Agriculture — — 3 4,264 — — 4 5,011 Commercial non-real estate — — — — — — — — Residential real estate — — — — — — — — Consumer — — — — — — — — Total — $ — 3 $ 4,264 — $ — 5 $ 6,023

Allowance for Loan and Lease _2

Allowance for Loan and Lease Losses (Tables)	6 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Summary of allowances for loan and lease losses	The following tables present the Company’s allowance for loan and lease losses roll forward for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, 2019 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance January 1, 2019 $ 16,348 $ 31,785 $ 12,093 $ 4,611 $ 430 $ 926 $ 66,193 Charge-offs (75 ) (5,767 ) (110 ) (310 ) (85 ) (249 ) (6,596 ) Recoveries 162 199 104 125 44 99 733 Provision (855 ) 7,508 962 (344 ) (15 ) 150 7,406 Impairment of ASC 310-30 loans 23 — — 244 — — 267 Ending balance March 31, 2019 $ 15,603 $ 33,725 $ 13,049 $ 4,326 $ 374 $ 926 $ 68,003 Three Months Ended March 31, 2018 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance January 1, 2018 $ 15,995 $ 24,750 $ 16,434 $ 5,475 $ 307 $ 1,062 $ 64,023 Charge-offs (1,268 ) (783 ) (1,605 ) (20 ) (62 ) (557 ) (4,295 ) Recoveries 61 125 88 27 20 190 511 Provision 4,077 152 813 (341 ) 14 281 4,996 Impairment (improvement) of ASC 310-30 loans 49 (115 ) — (30 ) — — (96 ) Ending balance March 31, 2018 $ 18,914 $ 24,129 $ 15,730 $ 5,111 $ 279 $ 976 $ 65,139 Six Months Ended March 31, 2019 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance October 1, 2018 $ 16,777 $ 28,121 $ 13,610 $ 4,749 $ 257 $ 1,026 $ 64,540 Charge-offs (946 ) (7,028 ) (1,471 ) (642 ) (334 ) (394 ) (10,815 ) Recoveries 259 357 228 287 128 131 1,390 Provision (68 ) 12,275 682 (369 ) 323 163 13,006 (Improvement) impairment of ASC 310-30 loans (419 ) — — 301 — — (118 ) Ending balance March 31, 2019 $ 15,603 $ 33,725 $ 13,049 $ 4,326 $ 374 $ 926 $ 68,003 Six Months Ended March 31, 2018 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Beginning balance January 1, 2018 $ 16,941 $ 25,757 $ 14,114 $ 5,347 $ 329 $ 1,015 $ 63,503 Charge-offs (1,597 ) (2,981 ) (2,844 ) (275 ) (116 ) (1,091 ) (8,904 ) Recoveries 209 172 209 117 42 334 1,083 Provision 3,322 1,296 4,251 (11 ) 24 718 9,600 Impairment (improvement) of ASC 310-30 loans 39 (115 ) — (67 ) — — (143 ) Ending balance March 31, 2018 $ 18,914 $ 24,129 $ 15,730 $ 5,111 $ 279 $ 976 $ 65,139 The following tables provide details regarding the allowance for loan and lease losses and balance by type of allowance as of March 31, 2019 and September 30, 2018 . These tables are presented net of unamortized discount on acquired loans and excludes loans of $835.8 million measured at fair value, loans held for sale of $3.6 million , and guaranteed loans of $153.5 million for March 31, 2019 and loans measured at fair value of $865.4 million , loans held for sale of $5.5 million , and guaranteed loans of $160.3 million for September 30, 2018 . As of March 31, 2019 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Allowance for loan and lease losses Individually evaluated for impairment $ 2,258 $ 14,281 $ 3,338 $ 1,562 $ 123 $ — $ 21,562 Collectively evaluated for impairment 13,085 19,179 9,711 2,201 251 926 45,353 ASC 310-30 loans 260 265 — 563 — — 1,088 Total allowance $ 15,603 $ 33,725 $ 13,049 $ 4,326 $ 374 $ 926 $ 68,003 Financing Receivables Individually evaluated for impairment $ 32,653 $ 159,497 $ 22,883 $ 6,632 $ 209 $ — $ 221,874 Collectively evaluated for impairment 4,395,621 1,758,897 1,492,803 765,417 43,616 46,163 8,502,517 ASC 310-30 loans 27,296 2,827 403 35,038 500 — 66,064 Loans Outstanding $ 4,455,570 $ 1,921,221 $ 1,516,089 $ 807,087 $ 44,325 $ 46,163 $ 8,790,455 As of September 30, 2018 Commercial Real Estate Agriculture Commercial Non-Real Estate Residential Real Estate Consumer Other Total (dollars in thousands) Allowance for loan and lease losses Individually evaluated for impairment $ 3,668 $ 9,590 $ 4,508 $ 2,210 $ 61 $ — $ 20,037 Collectively evaluated for impairment 12,430 18,266 9,102 2,277 196 1,026 43,297 ASC 310-30 loans 679 265 — 262 — — 1,206 Total allowance $ 16,777 $ 28,121 $ 13,610 $ 4,749 $ 257 $ 1,026 $ 64,540 Financing Receivables Individually evaluated for impairment $ 40,900 $ 137,225 $ 23,082 $ 6,686 $ 161 $ — $ 208,054 Collectively evaluated for impairment 4,053,712 1,823,947 1,364,511 780,047 48,711 46,487 8,117,415 ASC 310-30 loans 27,001 2,815 416 40,025 588 — 70,845 Loans Outstanding $ 4,121,613 $ 1,963,987 $ 1,388,009 $ 826,758 $ 49,460 $ 46,487 $ 8,396,314

Accounting for Certain Loans _2

Accounting for Certain Loans Acquired with Deteriorated Credit Quality (Tables)	6 Months Ended
	Mar. 31, 2019
Receivables [Abstract]
Schedule of troubled debt restructurings	The re-assessment of purchased credit impaired loans resulted in the following changes in the accretable yield during the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Balance at beginning of period $ 35,493 $ 41,918 $ 34,973 $ 44,131 Accretion (2,188 ) (3,664 ) (4,343 ) (7,045 ) Reclassification from (to) nonaccretable difference 375 (413 ) 3,050 755 Balance at end of period $ 33,680 $ 37,841 $ 33,680 $ 37,841
Schedule of impaired loans	The following table presents the Company’s impaired loans. This table excludes purchased credit impaired loans and loans measured at fair value with changes in fair value reported in earnings of $835.8 million at March 31, 2019 and $865.4 million at September 30, 2018 . March 31, 2019 September 30, 2018 Recorded Investment Unpaid Principal Balance Related Allowance Recorded Investment Unpaid Principal Balance Related Allowance (dollars in thousands) Impaired loans: With an allowance recorded: Commercial real estate $ 22,058 $ 22,102 $ 2,258 $ 25,136 $ 25,223 $ 3,668 Agriculture 67,476 81,601 14,281 60,053 76,874 9,590 Commercial non-real estate 14,214 16,933 3,338 14,177 17,241 4,508 Residential real estate 3,093 3,678 1,562 4,509 5,153 2,210 Consumer 209 213 123 160 165 61 Total impaired loans with an allowance recorded 107,050 124,527 21,562 104,035 124,656 20,037 With no allowance recorded: Commercial real estate 10,595 50,487 — 15,764 58,141 — Agriculture 92,021 102,968 — 77,172 80,355 — Commercial non-real estate 8,669 17,809 — 8,905 18,047 — Residential real estate 3,539 5,969 — 2,177 4,574 — Consumer — 117 — 1 118 — Total impaired loans with no allowance recorded 114,824 177,350 — 104,019 161,235 — Total impaired loans $ 221,874 $ 301,877 $ 21,562 $ 208,054 $ 285,891 $ 20,037 The following table presents the average recorded investment on impaired loans and interest income recognized on impaired loans for the three and six months ended March 31, 2019 and 2018 . Three Months Ended Six Months Ended March 31, 2019 March 31, 2018 March 31, 2019 March 31, 2018 Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status Average Recorded Investment Interest Income Recognized While on Impaired Status (dollars in thousands) Commercial real estate $ 34,475 $ 345 $ 66,577 $ 477 $ 36,616 $ 697 $ 56,875 $ 2,053 Agriculture 151,021 2,203 121,062 1,189 146,423 3,202 124,200 2,171 Commercial non-real estate 22,556 312 30,350 325 22,731 678 30,878 776 Residential real estate 6,724 93 7,578 116 6,711 182 7,636 281 Consumer 237 6 238 4 212 11 256 8 Total $ 215,013 $ 2,959 $ 225,805 $ 2,111 $ 212,693 $ 4,770 $ 219,845 $ 5,289 The following table provides purchased credit impaired loans at March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Outstanding Balance ¹ Recorded Investment ² Carrying Value ³ Outstanding Balance ¹ Recorded Investment ² Carrying Value ³ (dollars in thousands) Commercial real estate $ 99,468 $ 27,296 $ 27,036 $ 100,761 $ 27,001 $ 26,322 Agriculture 4,622 2,827 2,562 4,841 2,815 2,551 Commercial non-real estate 7,419 403 403 7,475 416 416 Residential real estate 40,969 35,038 34,475 46,646 40,025 39,763 Consumer 555 500 500 656 588 588 Total lending $ 153,033 $ 66,064 $ 64,976 $ 160,379 $ 70,845 $ 69,640 1 Represents the legal balance of ASC 310-30 loans. 2 Represents the book balance of ASC 310-30 loans. 3 Represents the book balance of ASC 310-30 loans net of the related allowance for loan and lease losses.

FDIC Indemnification Asset (Tab

FDIC Indemnification Asset (Tables)	6 Months Ended
	Mar. 31, 2019
Banking and Thrift [Abstract]
Summary of FDIC indemnification asset activity	The following table represents a summary of the activity related to the FDIC indemnification asset for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Balance at beginning of period $ 1,950 $ 4,692 $ 2,502 $ 5,704 Amortization (360 ) (732 ) (853 ) (1,750 ) Changes in expected reimbursements from FDIC for changes in expected credit losses (13 ) (15 ) (13 ) (33 ) Changes in reimbursable expenses (16 ) (456 ) (41 ) (662 ) (Reimbursements) payments of covered losses (from) to the FDIC (9 ) 189 (43 ) 419 Balance at end of period $ 1,552 $ 3,678 $ 1,552 $ 3,678

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and September 30, 2018 . March 31, 2019 September 30, 2018 Notional Amount Gross Asset Gross Liability Notional Amount Gross Asset Gross Liability (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps Financial institution counterparties $ 1,237,398 $ 4,394 $ (12,824 ) $ 1,082,630 $ 22,696 $ (2,231 ) Customer counterparties 430,434 20,676 (40 ) 217,066 1,533 (2,160 ) Mortgage loan commitments 22,463 21 — 22,195 — (28 ) Mortgage loan forward sale contracts 25,103 — (21 ) 27,408 28 — Total $ 1,715,398 $ 25,091 $ (12,885 ) $ 1,349,299 $ 24,257 $ (4,419 )
Summary of offsetting assets	The following tables provide information on the Company's netting adjustments as of March 31, 2019 and September 30, 2018 . Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of March 31, 2019 Total Derivative Assets $ 25,091 $ (3,198 ) $ 3,950 $ 25,843 Total Derivative Liabilities ¹ $ (12,885 ) $ 3,198 $ 9,629 $ (58 ) 1 There was an additional $11.4 million of collateral held for initial margin with our Futures Clearing Merchant for clearing derivatives at March 31, 2019 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, 2018 Total Derivative Assets $ 24,257 $ (2,231 ) $ (20,115 ) $ 1,911 Total Derivative Liabilities ¹ (4,419 ) 2,231 — (2,188 ) 1 There was an additional $6.2 million of collateral held for initial margin with our Futures Clearing Merchant for clearing derivatives at September 30, 2018 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 March 31, 2019 and September 30, 2018 . Gross Fair Value Fair Value Offset Amount Cash Collateral Net Amount Presented on the Consolidated Balance Sheet (dollars in thousands) As of March 31, 2019 Total Derivative Assets $ 25,091 $ (3,198 ) $ 3,950 $ 25,843 Total Derivative Liabilities ¹ $ (12,885 ) $ 3,198 $ 9,629 $ (58 ) 1 There was an additional $11.4 million of collateral held for initial margin with our Futures Clearing Merchant for clearing derivatives at March 31, 2019 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, 2018 Total Derivative Assets $ 24,257 $ (2,231 ) $ (20,115 ) $ 1,911 Total Derivative Liabilities ¹ (4,419 ) 2,231 — (2,188 ) 1 There was an additional $6.2 million of collateral held for initial margin with our Futures Clearing Merchant for clearing derivatives at September 30, 2018 and is included in other assets in the consolidated balance sheets.
Schedule of derivative instruments, effect on other comprehensive income	The effect of derivatives on the consolidated statements of income for the three and six months ended March 31, 2019 and 2018 was as follows. Amount of (Loss) Gain Recognized in Consolidated Statements of Income Three Months Ended March 31, Six Months Ended March 31, Location of (Loss) Gain Recognized in Consolidated Statements of Income 2019 2018 2019 2018 (dollars in thousands) Derivatives not designated as hedging instruments: Interest rate swaps Net realized and unrealized (loss) gain on derivatives $ (11,032 ) $ 14,282 $ (29,348 ) $ 21,509 Mortgage loan commitments Net realized and unrealized (loss) gain on derivatives 9 2 21 3 Mortgage loan forward sale contracts Net realized and unrealized (loss) gain on derivatives (9 ) (2 ) (21 ) (3 )

The Fair Value Option for Cer_2

The Fair Value Option for Certain Loans (Tables)	6 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Summary of the fair value option	Changes in fair value for items for which the fair value option has been elected and the line items in which these changes are reported within the consolidated statements of income are as follows for the three and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 Noninterest Income (Loss) Total Changes in Fair Value Noninterest Income (Loss) Total Changes in Fair Value Noninterest Income (Loss) Total Changes in Fair Value Noninterest Income (Loss) Total Changes in Fair Value (dollars in thousands) Long-term loans $ 14,018 $ 14,018 $ (14,838 ) $ (14,838 ) $ 33,234 $ 33,234 $ (23,502 ) $ (23,502 )

Core Deposits and Other Intan_2

Core Deposits and Other Intangibles (Tables)	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and September 30, 2018 . Core Deposit Intangible Brand Other Total (dollars in thousands) As of March 31, 2019 Gross carrying amount $ 7,339 $ 8,464 $ 538 $ 16,341 Accumulated amortization (3,083 ) (6,110 ) (224 ) (9,417 ) Net intangible assets $ 4,256 $ 2,354 $ 314 $ 6,924 As of September 30, 2018 Gross carrying amount $ 7,339 $ 8,464 $ 538 $ 16,341 Accumulated amortization (2,610 ) (5,828 ) (191 ) (8,629 ) Net intangible assets $ 4,729 $ 2,636 $ 347 $ 7,712
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 2019 $ 750 2020 1,430 2021 1,334 2022 1,249 2023 967 2024 and thereafter 1,194 Total $ 6,924

Securities Sold Under Agreeme_2

Securities Sold Under Agreements to Repurchase (Tables)	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and September 30, 2018 . March 31, 2019 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 62,537 — — — 62,537 Total repurchase agreements $ 62,537 $ — $ — $ — $ 62,537 September 30, 2018 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 90,907 — — — 90,907 Total repurchase agreements $ 90,907 $ — $ — $ — $ 90,907

FHLB Advances and Other Borro_2

FHLB Advances and Other Borrowings (Tables)	6 Months Ended
	Mar. 31, 2019
Federal Home Loan Banks [Abstract]
Schedule of FHLB advances and other borrowings	FHLB advances and other borrowings consist of the following at March 31, 2019 and September 30, 2018 . March 31, September 30, 2019 2018 (dollars in thousands) Short-term borrowings: FHLB fed funds advance, matured $ — $ 100,000 Long-term borrowings: Notes payable to FHLB, interest rates from 2.68% to 3.66% and maturity dates from March 2021 to September 2024, collateralized by real estate loans, with various call dates at the option of the FHLB 275,000 175,000 Total $ 275,000 $ 275,000
Schedule of FHLB advances and other borrowings by maturity date	As of March 31, 2019 , 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 2019 $ — 2020 — 2021 70,000 2022 60,000 2023 85,000 2024 and thereafter 60,000 Total $ 275,000

Subordinated Debentures and S_2

Subordinated Debentures and Subordinated Notes Payable (Tables)	6 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Summary of subordinated debentures and subordinated notes payable	Subordinated debentures and subordinated notes payable are summarized as follows. March 31, 2019 September 30, 2018 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 (2,294 ) (2,317 ) Total junior subordinated debentures payable, net of fair value adjustment 73,626 73,603 Subordinated notes payable Fixed to floating rate, 4.875% per annum 35,000 35,000 Less: unamortized debt issuance costs (98 ) (135 ) Total subordinated notes payable 34,902 34,865 Total subordinated debentures and subordinated notes payable $ 108,528 $ 108,468 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)	6 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [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 March 31, 2019 and September 30, 2018 . The number of performance shares granted in the following table are reflected at the amount of achievement of the pre-established targets. March 31, 2019 September 30, 2018 Common Weighted-Average Grant Date Fair Value Common Weighted-Average Grant Date Fair Value Restricted Shares Restricted shares, beginning of fiscal year 163,287 $ 37.86 180,337 $ 33.06 Granted 106,364 37.29 89,376 41.07 Vested (74,242 ) 38.65 (97,682 ) 32.11 Forfeited (641 ) 39.53 (8,744 ) 35.99 Canceled — — — — Restricted shares, end of period 194,768 $ 37.24 163,287 $ 37.86 Vested, but not issuable at end of period 50,770 $ 33.88 39,514 $ 32.90 Performance Shares Performance shares, beginning of fiscal year 175,196 $ 36.29 133,604 $ 33.39 Granted 70,107 28.55 53,682 29.52 Vested (59,803 ) 30.78 (7,017 ) 18.00 Forfeited (93 ) 37.72 (5,073 ) 37.75 Canceled — — — — Performance shares, end of period 185,407 $ 38.50 175,196 $ 36.29 Vested, but not issuable at end of period 5,612 $ 18.00 5,612 $ 18.00

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Mar. 31, 2019
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 March 31, 2019 and September 30, 2018 . Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of March 31, 2019 U.S. Treasury securities $ 93,819 $ 93,819 $ — $ — Mortgage-backed securities 1,605,616 — 1,605,616 — States and political subdivision securities 62,870 — 61,559 1,311 Other 1,000 — 1,000 — Total securities available for sale $ 1,763,305 $ 93,819 $ 1,668,175 $ 1,311 Derivatives-assets $ 25,843 $ — $ 25,843 $ — Derivatives-liabilities 58 — 58 — Fair value loans 835,822 — 835,822 — Loan servicing rights 2,674 — — 2,674 As of September 30, 2018 U.S. Treasury securities $ 167,172 $ 167,172 $ — $ — Mortgage-backed securities 1,149,707 — 1,149,707 — States and political subdivision securities 67,775 — 66,805 970 Other 996 — 996 — Total securities available for sale $ 1,385,650 $ 167,172 $ 1,217,508 $ 970 Derivatives-assets $ 1,911 $ — $ 1,911 $ — Derivatives-liabilities 2,188 — 2,188 — Fair value loans 865,386 — 865,386 — Loan servicing rights 3,087 — — 3,087
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 and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands) Other securities available for sale Balance, beginning of period $ 961 $ 965 $ 970 $ 1,069 Additions 350 — 350 — Principal paydown — — (9 ) (104 ) Balance, end of period $ 1,311 $ 965 $ 1,311 $ 965 Loan servicing rights Balance, beginning of period $ 2,862 $ 3,799 $ 3,087 $ 4,074 Realized and unrealized loss ¹ (188 ) (213 ) (413 ) (488 ) Balance, end of period $ 2,674 $ 3,586 $ 2,674 $ 3,586 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 tables present 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 March 31, 2019 and September 30, 2018 . Fair Value Level 1 Level 2 Level 3 (dollars in thousands) As of March 31, 2019 Other repossessed property $ 31,834 $ — $ — $ 31,834 Impaired loans 200,312 — — 200,312 Loans held for sale, at lower of cost or fair value 3,648 — 3,648 — Property held for sale 3,216 — — 3,216 As of September 30, 2018 Other repossessed property $ 22,225 $ — $ — $ 22,225 Impaired loans 188,017 — — 188,017 Loans held for sale, at lower of cost or fair value 5,456 — 5,456 — Property held for sale 1,104 — — 1,104
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 March 31, 2019 were as follows. Fair Value of Assets / (Liabilities) at March 31, 2019 Valuation Unobservable Range Weighted (dollars in thousands) Other repossessed property $ 31,834 Appraisal value Property specific adjustment N/A N/A Impaired loans 200,312 Appraisal value Property specific adjustment N/A N/A Property held for sale 3,216 Appraisal value Property specific adjustment N/A N/A
Schedule of fair values for balance sheet instruments	Fair values for on-balance sheet instruments as of March 31, 2019 and September 30, 2018 are as follows. March 31, 2019 September 30, 2018 Level in Fair Value Hierarchy Carrying Amount Fair Carrying Amount Fair (dollars in thousands) Assets Cash and cash equivalents Level 1 $ 282,638 $ 282,638 $ 298,696 $ 298,696 Loans, net, excluding fair valued loans, loans held for sale and impaired loans ¹ Level 3 8,731,128 8,721,910 8,357,065 8,231,829 Liabilities Time deposits Level 2 2,087,558 2,086,538 1,847,078 1,848,550 FHLB advances and other borrowings Level 2 275,000 280,374 275,000 275,797 Securities sold under repurchase agreements Level 2 62,537 62,537 90,907 90,907 Subordinated debentures and subordinated notes payable Level 2 108,528 102,285 108,468 107,841 1 Includes $13.5 million and $13.0 million of net deferred loan fees at March 31, 2019 and September 30, 2018, respectively, of which carrying value approximates fair value.

Earnings per Share (Tables)

Earnings per Share (Tables)	6 Months Ended
	Mar. 31, 2019
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 and six months ended March 31, 2019 and 2018 . Three Months Ended March 31, Six Months Ended March 31, 2019 2018 2019 2018 (dollars in thousands, except per share data) Net income $ 44,511 $ 40,532 $ 90,297 $ 69,762 Weighted average common shares outstanding 56,994,817 58,941,315 57,484,838 58,921,972 Dilutive effect of stock based compensation 79,857 204,802 72,146 194,951 Weighted average common shares outstanding for diluted earnings per share calculation 57,074,674 59,146,117 57,556,984 59,116,923 Basic earnings per share $ 0.78 $ 0.69 $ 1.57 $ 1.18 Diluted earnings per share $ 0.78 $ 0.69 $ 1.57 $ 1.18

Nature of Operations and Summ_4

Nature of Operations and Summary of Significant Policies Nature of Operations ans Summary of Significant Policies - Disaggregation of Noninterest Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Noninterest income from contracts with customers within the scope of ASC Topic 606	$ 13,444	$ 17,733	$ 27,955	$ 33,745
Noninterest income within the scope of other GAAP Topics	4,779	1,009	6,988	1,671
Total noninterest income	18,223	18,742	34,943	35,416
Service charges and other fees
Disaggregation of Revenue [Line Items]
Noninterest income from contracts with customers within the scope of ASC Topic 606	10,209	12,047	21,897	25,224
Wealth management fees
Disaggregation of Revenue [Line Items]
Noninterest income from contracts with customers within the scope of ASC Topic 606	2,117	2,335	4,358	4,519
Other
Disaggregation of Revenue [Line Items]
Noninterest income from contracts with customers within the scope of ASC Topic 606	$ 1,118	$ 3,351	$ 1,700	$ 4,002

Nature of Operations and Summ_5

Nature of Operations and Summary of Significant Policies - Narrative (Details) - $ / shares	Apr. 25, 2019	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Dividends Payable [Line Items]
Common stock dividends declared (in dollars per share)		$ 0.25	$ 0.20	$ 0.50	$ 0.40
Subsequent event
Dividends Payable [Line Items]
Common stock dividends declared (in dollars per share)	$ 0.3

New Accounting Pronouncements -

New Accounting Pronouncements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ (13,444)	$ (17,733)	$ (27,955)	$ (33,745)
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue	$ 2,000		$ 3,700

Securities Available for Sale -

Securities Available for Sale - Narrative (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2019USD ($)security	Mar. 31, 2018USD ($)	Mar. 31, 2019USD ($)security	Mar. 31, 2018USD ($)	Sep. 30, 2018USD ($)security
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of securities available for sale	$ 0	$ 25,000,000	$ 97,212,000	$ 25,206,000
Gross gains realized	0	0	0	0
Gross loss realized	0	0	500,000	500,000
Other than temporary impairment losses recognized in earnings	0	$ 0	0	$ 0
Securities pledged as collateral	$ 945,900,000		$ 945,900,000		$ 787,400,000
Percentage of investment portfolio in continuous loss position (as a percent)	62.00%		62.00%		98.00%
Number of securities in an unrealized loss position (securities) | security	293		293		390

Securities Available for Sale_2

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	$ 1,774,403	$ 1,427,454
Gross Unrealized Gains	7,860	39
Gross Unrealized Losses	(18,958)	(41,843)
Estimated Fair Value	1,763,305	1,385,650
U.S. Treasury securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	93,696	168,394
Gross Unrealized Gains	419	0
Gross Unrealized Losses	(296)	(1,222)
Estimated Fair Value	93,819	167,172
States and political subdivision securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	63,400	69,566
Gross Unrealized Gains	151	4
Gross Unrealized Losses	(681)	(1,795)
Estimated Fair Value	62,870	67,775
Other
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	1,006	1,006
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6)	(10)
Estimated Fair Value	1,000	996
Government National Mortgage Association | Mortgage-backed Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	491,888	442,458
Gross Unrealized Gains	1,811	35
Gross Unrealized Losses	(9,909)	(16,335)
Estimated Fair Value	483,790	426,158
Federal Home Loan Mortgage Corporation | Mortgage-backed Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	438,605	297,380
Gross Unrealized Gains	3,697	0
Gross Unrealized Losses	(2,839)	(7,055)
Estimated Fair Value	439,463	290,325
Federal National Mortgage Association | Mortgage-backed Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	303,643	188,192
Gross Unrealized Gains	1,268	0
Gross Unrealized Losses	(2,386)	(6,081)
Estimated Fair Value	302,525	182,111
Small Business Assistance Program | Mortgage-backed Securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized Cost	382,165	260,458
Gross Unrealized Gains	514	0
Gross Unrealized Losses	(2,841)	(9,345)
Estimated Fair Value	$ 379,838	$ 251,113

Securities Available for Sale_3

Securities Available for Sale - Schedule of Amortized Cost and Fair Value of Investments by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Amortized Cost
Due in one year or less	$ 36,309	$ 111,842
Due after one year through five years	111,862	114,920
Due after five years through ten years	8,803	11,076
Due after ten years	122	122
Amortized Cost	157,096	237,960
Estimated Fair Value
Due in one year or less	36,153	111,221
Due after one year through five years	111,756	113,069
Due after five years through ten years	8,658	10,535
Due after ten years	122	122
Estimated Fair Value	156,689	234,947
Amortized Cost	1,774,403	1,427,454
Estimated Fair Value	1,763,305	1,385,650
Securities without contractual maturities, Amortized Cost	1,006	1,006
Securities without contractual maturities, Fair Value	1,000	996
Mortgage-backed securities
Estimated Fair Value
Amortized Cost	1,616,301	1,188,488
Estimated Fair Value	$ 1,605,616	$ 1,149,707

Securities Available for Sale_4

Securities Available for Sale - Schedule of Gross Unrealized Losses on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 months, Estimated Fair Value	$ 126,015	$ 608,379
12 months or more, Estimated Fair Value	960,155	751,669
Estimated Fair Value	1,086,170	1,360,048
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	18,490	31,934
12 months or more, Unrealized Losses	468	9,909
Unrealized Losses	18,958	41,843
U.S. Treasury securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 months, Estimated Fair Value	0	167,172
12 months or more, Estimated Fair Value	44,232	0
Estimated Fair Value	44,232	167,172
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	296	0
12 months or more, Unrealized Losses	0	1,222
Unrealized Losses	296	1,222
Mortgage-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 months, Estimated Fair Value	126,015	416,677
12 months or more, Estimated Fair Value	865,274	709,387
Estimated Fair Value	991,289	1,126,064
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	17,507	30,389
12 months or more, Unrealized Losses	468	8,427
Unrealized Losses	17,975	38,816
States and political subdivision securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 months, Estimated Fair Value	0	23,534
12 months or more, Estimated Fair Value	49,649	42,282
Estimated Fair Value	49,649	65,816
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	681	1,545
12 months or more, Unrealized Losses	0	250
Unrealized Losses	681	1,795
Other
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract]
Less than 12 months, Estimated Fair Value	0	996
12 months or more, Estimated Fair Value	1,000	0
Estimated Fair Value	1,000	996
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Unrealized Losses	6	0
12 months or more, Unrealized Losses	0	10
Unrealized Losses	$ 6	$ 10

Loans - Narrative (Details)

Loans - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans covered by a FDIC loss share agreement	$ 36,975		$ 36,975		$ 42,627
Loan held for sale	3,648		3,648		5,456
Loans and written loan commitments at fair value under the fair value option	835,822		835,822		865,386
Unamortized discount on acquired loans	13,500		13,500		13,000
Loans in process	(1,000)		(1,000)		(1,500)
Loans guaranteed by U.S. Government Agencies	8,790,455		8,790,455		8,396,314
Principal balances of residential real estate loans sold	46,800	$ 67,600	100,700	$ 117,800
Loans greater than 90 days past due and still accruing interest	0		0		200
Valuation adjustments made to repossessed properties	100	700	2,000	700
Specific reserves included in the allowance for loan losses for TDRs	7,400		7,400		9,200
Troubled debt restructuring, commitments to lend additional funds	600		600		300
Transfers out of troubled debt restructuring status	0	$ 100	0	$ 600
Loans Guaranteed by US Government Authorities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans guaranteed by U.S. Government Agencies	$ 164,500		$ 164,500		$ 168,600

Loans - Schedule of Loans Recei

Loans - Schedule of Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	$ 9,798,638	$ 9,445,750
Less: Unamortized discount on acquired loans	(15,255)	(18,283)
Unearned net deferred fees and costs and loans in process	(12,472)	(11,543)
Net loans	9,770,911	9,415,924
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	5,049,792	4,629,330
Agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	2,121,872	2,182,688
Commercial non-real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	1,721,095	1,699,987
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	815,212	837,569
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	44,504	49,689
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total financing receivables, gross	$ 46,163	$ 46,487

Loans - Schedule of the Company

Loans - Schedule of the Company's Nonaccrual Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans, excluding loans covered under FDIC loss-sharing arrangements	$ 119,154	$ 140,566
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans, excluding loans covered under FDIC loss-sharing arrangements	17,929	22,871
Agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans, excluding loans covered under FDIC loss-sharing arrangements	91,771	107,198
Commercial non-real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans, excluding loans covered under FDIC loss-sharing arrangements	6,868	6,887
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans, excluding loans covered under FDIC loss-sharing arrangements	2,499	3,549
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans, excluding loans covered under FDIC loss-sharing arrangements	$ 87	$ 61

Loans - Schedule of the Composi

Loans - Schedule of the Composition of the Loan Portfolio by Internal Risk Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	$ 8,910,588	$ 8,519,454
Loans covered by a FDIC loss share agreement	36,975	42,627
Total	8,947,563	8,562,081
Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	8,405,503	7,995,099
Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	284,963	316,915
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	218,570	205,031
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,552	2,409
Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	4,535,770	4,202,741
Loans covered by a FDIC loss share agreement	0	0
Total	4,535,770	4,202,741
Commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	4,455,347	4,108,314
Commercial real estate | Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	47,424	53,150
Commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	32,938	41,184
Commercial real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	61	93
Commercial real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Agriculture
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,942,385	1,986,890
Loans covered by a FDIC loss share agreement	0	0
Total	1,942,385	1,986,890
Agriculture | Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,584,602	1,610,291
Agriculture | Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	199,585	239,392
Agriculture | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	158,061	137,205
Agriculture | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	137	2
Agriculture | Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Commercial non-real estate
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,567,536	1,443,315
Loans covered by a FDIC loss share agreement	0	0
Total	1,567,536	1,443,315
Commercial non-real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,512,883	1,401,418
Commercial non-real estate | Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	32,402	19,503
Commercial non-real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	20,926	20,117
Commercial non-real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	1,325	2,277
Commercial non-real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	774,409	790,561
Loans covered by a FDIC loss share agreement	36,975	42,627
Total	811,384	833,188
Residential real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	762,495	779,610
Residential real estate | Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	5,450	4,548
Residential real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	6,435	6,366
Residential real estate | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	29	37
Residential real estate | Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Consumer
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	44,325	49,460
Loans covered by a FDIC loss share agreement	0	0
Total	44,325	49,460
Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	44,013	48,979
Consumer | Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	102	322
Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	210	159
Consumer | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Consumer | Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Other
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	46,163	46,487
Loans covered by a FDIC loss share agreement	0	0
Total	46,163	46,487
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	46,163	46,487
Other | Watchlist
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Other | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	0	0
Other | Loss
Financing Receivable, Recorded Investment [Line Items]
Total financing receivables	$ 0	$ 0

Loans - Schedule of Past Due Lo

Loans - Schedule of Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	$ 8,910,588	$ 8,519,454
Loans covered by FDIC loss sharing agreements	36,975	42,627
Total	8,947,563	8,562,081
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	4,535,770	4,202,741
Loans covered by FDIC loss sharing agreements	0	0
Total	4,535,770	4,202,741
Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	1,942,385	1,986,890
Loans covered by FDIC loss sharing agreements	0	0
Total	1,942,385	1,986,890
Commercial non-real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	1,567,536	1,443,315
Loans covered by FDIC loss sharing agreements	0	0
Total	1,567,536	1,443,315
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	774,409	790,561
Loans covered by FDIC loss sharing agreements	36,975	42,627
Total	811,384	833,188
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	44,325	49,460
Loans covered by FDIC loss sharing agreements	0	0
Total	44,325	49,460
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	46,163	46,487
Loans covered by FDIC loss sharing agreements	0	0
Total	46,163	46,487
Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	80,097	73,096
Loans covered by FDIC loss sharing agreements	2,247	734
Total	82,344	73,830
Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	8,665	10,606
Past Due | Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	57,618	54,864
Past Due | Commercial non-real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	9,747	4,635
Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	3,844	2,860
Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	223	131
Past Due | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	0	0
Past Due | 30-59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	19,319	3,710
Loans covered by FDIC loss sharing agreements	1,955	30
Total	21,274	3,740
Past Due | 30-59 Days Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	3,051	920
Past Due | 30-59 Days Past Due | Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	11,558	1,243
Past Due | 30-59 Days Past Due | Commercial non-real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	2,161	551
Past Due | 30-59 Days Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	2,341	913
Past Due | 30-59 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	208	83
Past Due | 30-59 Days Past Due | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	0	0
Past Due | 60-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	13,929	2,856
Loans covered by FDIC loss sharing agreements	78	233
Total	14,007	3,089
Past Due | 60-89 Days Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	95	551
Past Due | 60-89 Days Past Due | Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	8,985	2,042
Past Due | 60-89 Days Past Due | Commercial non-real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	4,134	16
Past Due | 60-89 Days Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	700	200
Past Due | 60-89 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	15	47
Past Due | 60-89 Days Past Due | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	0	0
Past Due | 90 Days or Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	46,849	66,530
Loans covered by FDIC loss sharing agreements	214	471
Total	47,063	67,001
Past Due | 90 Days or Greater Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	5,519	9,135
Past Due | 90 Days or Greater Past Due | Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	37,075	51,579
Past Due | 90 Days or Greater Past Due | Commercial non-real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	3,452	4,068
Past Due | 90 Days or Greater Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	803	1,747
Past Due | 90 Days or Greater Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	0	1
Past Due | 90 Days or Greater Past Due | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	0	0
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	8,830,491	8,446,358
Loans covered by FDIC loss sharing agreements	34,728	41,893
Total	8,865,219	8,488,251
Current | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	4,527,105	4,192,135
Current | Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	1,884,767	1,932,026
Current | Commercial non-real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	1,557,789	1,438,680
Current | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	770,565	787,701
Current | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	44,102	49,329
Current | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivables, net of unamortized discount on acquired loans	$ 46,163	$ 46,487

Loans - Schedule of Impaired Lo

Loans - Schedule of Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
With an allowance recorded:
Recorded Investment	$ 107,050		$ 107,050		$ 104,035
Unpaid Principal Balance	124,527		124,527		124,656
Related Allowance	21,562		21,562		20,037
With no allowance recorded:
Recorded Investment	114,824		114,824		104,019
Unpaid Principal Balance	177,350		177,350		161,235
Total Recorded Investment, Impaired Loans	221,874		221,874		208,054
Total Unpaid Principal Balance, Impaired Loans	301,877		301,877		285,891
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	215,013	$ 225,805	212,693	$ 219,845
Interest Income Recognized While on Impaired Status	2,959	2,111	4,770	5,289
Commercial real estate
With an allowance recorded:
Recorded Investment	22,058		22,058		25,136
Unpaid Principal Balance	22,102		22,102		25,223
Related Allowance	2,258		2,258		3,668
With no allowance recorded:
Recorded Investment	10,595		10,595		15,764
Unpaid Principal Balance	50,487		50,487		58,141
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	34,475	66,577	36,616	56,875
Interest Income Recognized While on Impaired Status	345	477	697	2,053
Agriculture
With an allowance recorded:
Recorded Investment	67,476		67,476		60,053
Unpaid Principal Balance	81,601		81,601		76,874
Related Allowance	14,281		14,281		9,590
With no allowance recorded:
Recorded Investment	92,021		92,021		77,172
Unpaid Principal Balance	102,968		102,968		80,355
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	151,021	121,062	146,423	124,200
Interest Income Recognized While on Impaired Status	2,203	1,189	3,202	2,171
Commercial non-real estate
With an allowance recorded:
Recorded Investment	14,214		14,214		14,177
Unpaid Principal Balance	16,933		16,933		17,241
Related Allowance	3,338		3,338		4,508
With no allowance recorded:
Recorded Investment	8,669		8,669		8,905
Unpaid Principal Balance	17,809		17,809		18,047
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	22,556	30,350	22,731	30,878
Interest Income Recognized While on Impaired Status	312	325	678	776
Residential real estate
With an allowance recorded:
Recorded Investment	3,093		3,093		4,509
Unpaid Principal Balance	3,678		3,678		5,153
Related Allowance	1,562		1,562		2,210
With no allowance recorded:
Recorded Investment	3,539		3,539		2,177
Unpaid Principal Balance	5,969		5,969		4,574
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	6,724	7,578	6,711	7,636
Interest Income Recognized While on Impaired Status	93	116	182	281
Consumer
With an allowance recorded:
Recorded Investment	209		209		160
Unpaid Principal Balance	213		213		165
Related Allowance	123		123		61
With no allowance recorded:
Recorded Investment	0		0		1
Unpaid Principal Balance	117		117		$ 118
Average recorded investment and interest income recognized on impaired loans:
Average Recorded Investment	237	238	212	256
Interest Income Recognized While on Impaired Status	$ 6	$ 4	$ 11	$ 8

Loans - Summary of Troubled Deb

Loans - Summary of Troubled Debt Restructurings on Accruing and Nonaccrual Financing Receivables (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019USD ($)contract	Mar. 31, 2018USD ($)contract	Mar. 31, 2019USD ($)contract	Mar. 31, 2018USD ($)contract	Sep. 30, 2018USD ($)
Accruing
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 17,243		$ 17,243		$ 19,783
Financing receivable, modifications, number of contracts | contract	0	3	1	3
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 6,146	$ 89	$ 6,146
Financing receivable, modifications, post-modification recorded investment	$ 0	$ 6,146	$ 89	$ 6,146
Change in recorded investment due to principal paydown at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to principal paydown at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to chargeoffs at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, post-modification recorded investment	0	$ 0	0	$ 0
Nonaccrual
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 48,541		$ 48,541		77,156
Financing receivable, modifications, number of contracts | contract	0	6	0	6
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 8,374	$ 0	$ 8,374
Financing receivable, modifications, post-modification recorded investment	$ 0	$ 8,374	$ 0	$ 8,374
Change in recorded investment due to principal paydown at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to principal paydown at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to principal paydown at time of modification, post-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, number of contracts | contract	0	0	0	0
Change in recorded investment due to chargeoffs at time of modification, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Change in recorded investment due to chargeoffs at time of modification, post-modification recorded investment	0	$ 0	0	$ 0
Commercial real estate | Accruing
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 1,930		$ 1,930		2,649
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	0	$ 0
Commercial real estate | Nonaccrual
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 1,068		$ 1,068		2,616
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	0	$ 0
Agriculture | Accruing
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 12,377		$ 12,377		13,248
Financing receivable, modifications, number of contracts | contract	0	2	0	2
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 6,073	$ 0	$ 6,073
Financing receivable, modifications, post-modification recorded investment	0	$ 6,073	0	$ 6,073
Agriculture | Nonaccrual
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 46,592		$ 46,592		73,741
Financing receivable, modifications, number of contracts | contract	0	6	0	6
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 8,374	$ 0	$ 8,374
Financing receivable, modifications, post-modification recorded investment	0	$ 8,374	0	$ 8,374
Commercial non-real estate | Accruing
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 2,498		$ 2,498		3,420
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	0	$ 0
Commercial non-real estate | Nonaccrual
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 705		$ 705		656
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	0	$ 0
Residential real estate | Accruing
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 347		$ 347		389
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	0	$ 0
Residential real estate | Nonaccrual
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 115		$ 115		143
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	0	$ 0	0	$ 0
Consumer | Accruing
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 91		$ 91		77
Financing receivable, modifications, number of contracts | contract	0	1	1	1
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 73	$ 89	$ 73
Financing receivable, modifications, post-modification recorded investment	0	$ 73	89	$ 73
Consumer | Nonaccrual
Financing Receivable, Modifications [Line Items]
Recorded value of TDR balance	$ 61		$ 61		$ 0
Financing receivable, modifications, number of contracts | contract	0	0	0	0
Financing receivable, modifications, pre-modification recorded investment	$ 0	$ 0	$ 0	$ 0
Financing receivable, modifications, post-modification recorded investment	$ 0	$ 0	$ 0	$ 0

Loans - Subsequent Defaults on

Loans - Subsequent Defaults on Modified Loans (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019USD ($)contract	Mar. 31, 2018USD ($)contract	Mar. 31, 2019USD ($)contract	Mar. 31, 2018USD ($)contract
Financing Receivable, Modifications [Line Items]
Number of Loans | contract	0	3	0	5
Recorded Investment | $	$ 0	$ 4,264	$ 0	$ 6,023
Commercial real estate
Financing Receivable, Modifications [Line Items]
Number of Loans | contract	0	0	0	1
Recorded Investment | $	$ 0	$ 0	$ 0	$ 1,012
Agriculture
Financing Receivable, Modifications [Line Items]
Number of Loans | contract	0	3	0	4
Recorded Investment | $	$ 0	$ 4,264	$ 0	$ 5,011
Commercial non-real estate
Financing Receivable, Modifications [Line Items]
Number of Loans | contract	0	0	0	0
Recorded Investment | $	$ 0	$ 0	$ 0	$ 0
Residential real estate
Financing Receivable, Modifications [Line Items]
Number of Loans | contract	0	0	0	0
Recorded Investment | $	$ 0	$ 0	$ 0	$ 0
Consumer
Financing Receivable, Modifications [Line Items]
Number of Loans | contract	0	0	0	0
Recorded Investment | $	$ 0	$ 0	$ 0	$ 0

Allowance for Loan and Lease _3

Allowance for Loan and Lease Losses - Summary of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	$ 66,193	$ 64,023	$ 64,540	$ 63,503
Charge-offs	(6,596)	(4,295)	(10,815)	(8,904)
Recoveries	733	511	1,390	1,083
Provision	7,406	4,996	13,006	9,600
Allowance for loan losses, ending balance	68,003	65,139	68,003	65,139
Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance			1,200
(Improvement) impairment of ASC 310-30 loans	267	(96)	(118)	(143)
Allowance for loan losses, ending balance	1,100		1,100
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	16,348	15,995	16,777	16,941
Charge-offs	(75)	(1,268)	(946)	(1,597)
Recoveries	162	61	259	209
Provision	(855)	4,077	(68)	3,322
Allowance for loan losses, ending balance	15,603	18,914	15,603	18,914
Commercial real estate | Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Improvement) impairment of ASC 310-30 loans	23	49	(419)	39
Agriculture
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	31,785	24,750	28,121	25,757
Charge-offs	(5,767)	(783)	(7,028)	(2,981)
Recoveries	199	125	357	172
Provision	7,508	152	12,275	1,296
Allowance for loan losses, ending balance	33,725	24,129	33,725	24,129
Agriculture | Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Improvement) impairment of ASC 310-30 loans	0	(115)	0	(115)
Commercial non-real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	12,093	16,434	13,610	14,114
Charge-offs	(110)	(1,605)	(1,471)	(2,844)
Recoveries	104	88	228	209
Provision	962	813	682	4,251
Allowance for loan losses, ending balance	13,049	15,730	13,049	15,730
Commercial non-real estate | Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Improvement) impairment of ASC 310-30 loans	0	0	0	0
Residential real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	4,611	5,475	4,749	5,347
Charge-offs	(310)	(20)	(642)	(275)
Recoveries	125	27	287	117
Provision	(344)	(341)	(369)	(11)
Allowance for loan losses, ending balance	4,326	5,111	4,326	5,111
Residential real estate | Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Improvement) impairment of ASC 310-30 loans	244	(30)	301	(67)
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	430	307	257	329
Charge-offs	(85)	(62)	(334)	(116)
Recoveries	44	20	128	42
Provision	(15)	14	323	24
Allowance for loan losses, ending balance	374	279	374	279
Consumer | Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Improvement) impairment of ASC 310-30 loans	0	0	0	0
Other
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	926	1,062	1,026	1,015
Charge-offs	(249)	(557)	(394)	(1,091)
Recoveries	99	190	131	334
Provision	150	281	163	718
Allowance for loan losses, ending balance	926	976	926	976
Other | Acquired receivables subject to ASC 310-30
Financing Receivable, Allowance for Credit Losses [Roll Forward]
(Improvement) impairment of ASC 310-30 loans	$ 0	$ 0	$ 0	$ 0

Allowance for Loan and Lease _4

Allowance for Loan and Lease Losses - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and written loan commitments at fair value under the fair value option	$ 835,822		$ 835,822			$ 865,386
Loan held for sale	3,648		3,648			5,456
Loans guaranteed by U.S. Government Agencies	8,790,455		8,790,455			8,396,314
Allowance for loan leases	68,003	$ 65,139	68,003	$ 65,139	$ 66,193	64,540	$ 64,023	$ 63,503
Unfunded loan commitment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Reserve for unfunded loan commitments	500		500			500
(Impairment) improvement of ASC 310-30 loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan leases	1,100		1,100			1,200
Net reversal of provision	267	$ (96)	(118)	$ (143)
Loans Guaranteed by US Government Authorities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans guaranteed by U.S. Government Agencies	164,500		164,500			168,600
Loans Guaranteed by US Government Authorities | Loans and Leases with Allowance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans guaranteed by U.S. Government Agencies	$ 153,500		$ 153,500			$ 160,300

Allowance for Loan and Lease _5

Allowance for Loan and Lease Losses - Summary of Allowance for Loan Losses by Type (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017
Allowance for loan and lease losses
Individually evaluated for impairment	$ 21,562		$ 20,037
Collectively evaluated for impairment	45,353		43,297
Total allowance	68,003	$ 66,193	64,540	$ 65,139	$ 64,023	$ 63,503
Financing Receivables
Individually evaluated for impairment	221,874		208,054
Collectively evaluated for impairment	8,502,517		8,117,415
Loans Outstanding	8,790,455		8,396,314
Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	1,088		1,206
Total allowance	1,100		1,200
Financing Receivables
ASC 310-30 loans	66,064		70,845
Commercial real estate
Allowance for loan and lease losses
Individually evaluated for impairment	2,258		3,668
Collectively evaluated for impairment	13,085		12,430
Total allowance	15,603	16,348	16,777	18,914	15,995	16,941
Financing Receivables
Individually evaluated for impairment	32,653		40,900
Collectively evaluated for impairment	4,395,621		4,053,712
Loans Outstanding	4,455,570		4,121,613
Commercial real estate | Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	260		679
Financing Receivables
ASC 310-30 loans	27,296		27,001
Agriculture
Allowance for loan and lease losses
Individually evaluated for impairment	14,281		9,590
Collectively evaluated for impairment	19,179		18,266
Total allowance	33,725	31,785	28,121	24,129	24,750	25,757
Financing Receivables
Individually evaluated for impairment	159,497		137,225
Collectively evaluated for impairment	1,758,897		1,823,947
Loans Outstanding	1,921,221		1,963,987
Agriculture | Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	265		265
Financing Receivables
ASC 310-30 loans	2,827		2,815
Commercial non-real estate
Allowance for loan and lease losses
Individually evaluated for impairment	3,338		4,508
Collectively evaluated for impairment	9,711		9,102
Total allowance	13,049	12,093	13,610	15,730	16,434	14,114
Financing Receivables
Individually evaluated for impairment	22,883		23,082
Collectively evaluated for impairment	1,492,803		1,364,511
Loans Outstanding	1,516,089		1,388,009
Commercial non-real estate | Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	0		0
Financing Receivables
ASC 310-30 loans	403		416
Residential real estate
Allowance for loan and lease losses
Individually evaluated for impairment	1,562		2,210
Collectively evaluated for impairment	2,201		2,277
Total allowance	4,326	4,611	4,749	5,111	5,475	5,347
Financing Receivables
Individually evaluated for impairment	6,632		6,686
Collectively evaluated for impairment	765,417		780,047
Loans Outstanding	807,087		826,758
Residential real estate | Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	563		262
Financing Receivables
ASC 310-30 loans	35,038		40,025
Consumer
Allowance for loan and lease losses
Individually evaluated for impairment	123		61
Collectively evaluated for impairment	251		196
Total allowance	374	430	257	279	307	329
Financing Receivables
Individually evaluated for impairment	209		161
Collectively evaluated for impairment	43,616		48,711
Loans Outstanding	44,325		49,460
Consumer | Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	0		0
Financing Receivables
ASC 310-30 loans	500		588
Other
Allowance for loan and lease losses
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	926		1,026
Total allowance	926	$ 926	1,026	$ 976	$ 1,062	$ 1,015
Financing Receivables
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	46,163		46,487
Loans Outstanding	46,163		46,487
Other | Acquired receivables subject to ASC 310-30
Allowance for loan and lease losses
ASC 310-30 loans	0		0
Financing Receivables
ASC 310-30 loans	$ 0		$ 0

Accounting for Certain Loans _3

Accounting for Certain Loans Acquired with Deteriorated Credit Quality - Schedule of Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 35,493	$ 41,918	$ 34,973	$ 44,131
Accretion	(2,188)	(3,664)	(4,343)	(7,045)
Reclassification from (to) nonaccretable difference	375	(413)	3,050	755
Balance at end of period	$ 33,680	$ 37,841	$ 33,680	$ 37,841

Accounting for Certain Loans _4

Accounting for Certain Loans Acquired with Deteriorated Credit Quality - Schedule of Impaired Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	$ 153,033	$ 160,379
Recorded Investment	66,064	70,845
Carrying Value	64,976	69,640
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	99,468	100,761
Recorded Investment	27,296	27,001
Carrying Value	27,036	26,322
Agriculture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	4,622	4,841
Recorded Investment	2,827	2,815
Carrying Value	2,562	2,551
Commercial non-real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	7,419	7,475
Recorded Investment	403	416
Carrying Value	403	416
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	40,969	46,646
Recorded Investment	35,038	40,025
Carrying Value	34,475	39,763
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding Balance	555	656
Recorded Investment	500	588
Carrying Value	$ 500	$ 588

FDIC Indemnification Asset - Su

FDIC Indemnification Asset - Summary of FDIC Indemnification Asset Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
FDIC Indemnification Asset [Roll Forward]
Balance at beginning of period	$ 1,950	$ 4,692	$ 2,502	$ 5,704
Amortization	(360)	(732)	(853)	(1,750)
Changes in expected reimbursements from FDIC for changes in expected credit losses	(13)	(15)	(13)	(33)
Changes in reimbursable expenses	(16)	(456)	(41)	(662)
(Reimbursements) payments of covered losses (from) to the FDIC	(9)	189	(43)	419
Balance at end of period	$ 1,552	$ 3,678	$ 1,552	$ 3,678

Derivative Financial Instrume_3

Derivative Financial Instruments - Schedule of Derivative Positions, Notional Amounts and Estimated Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Derivative [Line Items]
Gross Asset Fair Value	$ 25,091	$ 24,257
Gross Liability Fair Value	(12,885)	(4,419)
Not Designated as Hedging Instruments
Derivative [Line Items]
Notional Amount	1,715,398	1,349,299
Gross Asset Fair Value	25,091	24,257
Gross Liability Fair Value	(12,885)	(4,419)
Not Designated as Hedging Instruments | Interest rate swaps | Financial institution counterparties
Derivative [Line Items]
Notional Amount	1,237,398	1,082,630
Gross Asset Fair Value	4,394	22,696
Gross Liability Fair Value	(12,824)	(2,231)
Not Designated as Hedging Instruments | Interest rate swaps | Customer counterparties
Derivative [Line Items]
Notional Amount	430,434	217,066
Gross Asset Fair Value	20,676	1,533
Gross Liability Fair Value	(40)	(2,160)
Not Designated as Hedging Instruments | Mortgage loan commitments
Derivative [Line Items]
Notional Amount	22,463	22,195
Gross Asset Fair Value	21	0
Gross Liability Fair Value	0	(28)
Not Designated as Hedging Instruments | Mortgage loan forward sale contracts
Derivative [Line Items]
Notional Amount	25,103	27,408
Gross Asset Fair Value	0	28
Gross Liability Fair Value	$ (21)	$ 0

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets, gross amount	$ 25,091	$ 24,257
Derivative assets, fair value offset amount	(3,198)	(2,231)
Derivative assets, cash collateral	3,950	(20,115)
Derivative financial assets, net amount presented in Consolidated Balance Sheets	25,843	1,911
Derivative liabilities, gross amount	(12,885)	(4,419)
Derivative liabilities, fair value offset amount	3,198	2,231
Derivative liabilities, cash collateral	9,629	0
Derivative financial liabilities, net amount presented in Consolidated Balance Sheets	(58)	(2,188)
Collateral held for initial margin	$ 11,400	$ 6,200

Derivative Financial Instrume_5

Derivative Financial Instruments - Narrative (Details) - Risk Participation Agreements - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Derivative [Line Items]
Notional amount sold	$ 49.7	$ 37.4
Exposure from RPAs	$ 4.9	$ 0.4

Derivative Financial Instrume_6

Derivative Financial Instruments - Effect on the Consolidated Statement of Comprehensive Income (Details) - Noninterest income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Interest rate swaps
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	$ (11,032)	$ 14,282	$ (29,348)	$ 21,509
Mortgage loan commitments
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	9	2	21	3
Mortgage loan forward sale contracts
Derivative [Line Items]
Amount of (Loss) Gain Recognized in Consolidated Statements of Income	$ (9)	$ (2)	$ (21)	$ (3)

The Fair Value Option for Cer_3

The Fair Value Option for Certain Loans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Eligible item for the fair value option	$ (0.5)		$ (0.5)		$ (34.8)
Loans greater than 90 days past due or in nonaccrual status	20.7		20.7		30.9
Unpaid principal balance greater than 90 days past due or in nonaccrual status	24.5		24.5		34.7
Long-term loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total unpaid principal balance of long-term loans	836.3		836.3		$ 900.2
Total change in fair value attributable to changes in specific credit risk	$ (0.4)	$ 1.4	$ 0.8	$ 0.3

The Fair Value Option for Cer_4

The Fair Value Option for Certain Loans - Summary of the Fair Value Option (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of loans	$ 14,018	$ (14,838)	$ 33,234	$ (23,502)
Long-term loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of loans	14,018	(14,838)	33,234	(23,502)
Long-term loans | Noninterest Income (Loss)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of loans	$ 14,018	$ (14,838)	$ 33,234	$ (23,502)

Core Deposits and Other Intan_3

Core Deposits and Other Intangibles - Intangible Assets Amortization Expense (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 16,341	$ 16,341
Accumulated amortization	(9,417)	(8,629)
Total	6,924	7,712
Core Deposit Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	7,339	7,339
Accumulated amortization	(3,083)	(2,610)
Total	4,256	4,729
Brand Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	8,464	8,464
Accumulated amortization	(6,110)	(5,828)
Total	2,354	2,636
Other Intangible
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	538	538
Accumulated amortization	(224)	(191)
Total	$ 314	$ 347

Core Deposits and Other Intan_4

Core Deposits and Other Intangibles - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of core deposits and other intangibles	$ 0.4	$ 0.4	$ 0.8	$ 0.9

Core Deposits and Other Intan_5

Core Deposits and Other Intangibles - Schedule of Future Amortization Expense (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Remaining in 2019	$ 750
2020	1,430
2021	1,334
2022	1,249
2023	967
2024 and thereafter	1,194
Total	$ 6,924	$ 7,712

Securities Sold Under Agreeme_3

Securities Sold Under Agreements to Repurchase - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2019	Sep. 30, 2018
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Abstract]
Securities sold under agreements to repurchase	$ 101.2	$ 109.9
Securities sold under agreements to repurchase, fair value of collateral	$ 98.8	$ 104.6
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	Mar. 31, 2019	Sep. 30, 2018
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	$ 62,537	$ 90,907
Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	62,537	90,907
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	62,537	90,907
Overnight and Continuous | Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	62,537	90,907
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	Mar. 31, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Total	$ 275,000	$ 275,000
Notes payable to banks
Debt Instrument [Line Items]
Federal Home Loan Bank (FHLB) notes payable and fed funds advance	$ 275,000	175,000
Notes payable to banks | Minimum
Debt Instrument [Line Items]
Stated interest rate (as a percent)	2.68%
Notes payable to banks | Maximum
Debt Instrument [Line Items]
Stated interest rate (as a percent)	3.66%
Federal Home Loan Bank fed funds advance
Debt Instrument [Line Items]
Federal Home Loan Bank (FHLB) notes payable and fed funds advance	$ 0	$ 100,000

FHLB Advances and Other Borro_4

FHLB Advances and Other Borrowings - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Current borrowing capacity	$ 2,040	$ 1,820
Loans pledged to the Federal Home Loan Bank	4,480	3,950
Revolving Credit Facility | FRB Discount Window Loan
Debt Instrument [Line Items]
Borrowing capacity	1,640	1,590
Loans pledged to the Federal Reserve Board Discount Window	1,940	1,890
Letter of Credit | Federal Home Loan Bank
Debt Instrument [Line Items]
Borrowing capacity	$ 217	$ 150

FHLB Advances and Other Borro_5

FHLB Advances and Other Borrowings - Schedule of Due or Callable Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Total	$ 108,528	$ 108,468
FHLB Advances and Related Party Notes Payable
Debt Instrument [Line Items]
Remaining in 2019	0
2020	0
2021	70,000
2022	60,000
2023	85,000
2024 and thereafter	60,000
Total	$ 275,000

Subordinated Debentures and S_3

Subordinated Debentures and Subordinated Notes Payable - Junior Subordinated Deferrable Interest Debentures (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Mar. 31, 2019USD ($)trust$ / sharesshares	Sep. 30, 2018USD ($)
Debt Instrument [Line Items]
Total subordinated debentures and subordinated notes payable	$ 108,528	$ 108,468
Junior Subordinated Debt
Debt Instrument [Line Items]
Total subordinated debentures and subordinated notes payable	73,626	73,603
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
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 ($)	12 Months Ended
	Dec. 31, 2015	Mar. 31, 2019	Sep. 30, 2018
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%
Unamortized debt issuance costs		$ 98,000	$ 135,000
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	6 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2015	Sep. 30, 2018
Debt Instrument [Line Items]
Total	$ 108,528		$ 108,468
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	(2,294)		(2,317)
Total	73,626		73,603
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]
Less: unamortized debt issuance costs	$ (98)		(135)
Total	34,902		34,865
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, 4.875% per annum
Debt Instrument [Line Items]
Total subordinated debentures payable, amount outstanding	$ 35,000		$ 35,000
Stated interest rate (as a percent)	4.875%

Profit Sharing Plan - Profit Sh

Profit Sharing Plan - Profit Sharing Plan (Details) - Multiple employer 401(k) profit sharing plan $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2019USD ($)year	Mar. 31, 2018USD ($)
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, requisite service period			1 year
Defined contribution plan, minimum age requirement (years of age) | year			21
Contributions by the Company | $	$ 1.1	$ 1.2	$ 2.9	$ 3

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1.4	$ 1.4	$ 3.1	$ 2.9
Tax benefit from compensation expense	0.4	$ 0.4	0.8	$ 1
Share-based compensation, compensation cost not yet recognized	$ 8.3		$ 8.3
Share-based compensation, compensation cost not yet recognized, recognition period			2 years 8 months 1 day
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of vested stock awards			$ 1.8		$ 1.9

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Share and Performance-Based Stock Award Activity (Details) - $ / shares	6 Months Ended	12 Months Ended
	Mar. 31, 2019	Sep. 30, 2018
Restricted shares
Common Shares
Shares, beginning of fiscal year (in shares)	163,287	180,337
Granted (in shares)	106,364	89,376
Vested (in shares)	(74,242)	(97,682)
Forfeited (in shares)	(641)	(8,744)
Canceled (in shares)	0	0
Shares, end of period (in shares)	194,768	163,287
Vested, but not issuable at end of period (in shares)	50,770	39,514
Weighted-Average Grant Date Fair Value
Shares, beginning of fiscal year (in dollars per share)	$ 37.86	$ 33.06
Granted (in dollars per share)	37.29	41.07
Vested (in dollars per share)	38.65	32.11
Forfeited (in dollars per share)	39.53	35.99
Canceled (in dollars per share)	0	0
Shares, end of period (in dollars per share)	37.24	37.86
Vested, but not issuable at end of period (in dollars per share)	$ 33.88	$ 32.90
Performance shares
Common Shares
Shares, beginning of fiscal year (in shares)	175,196	133,604
Granted (in shares)	70,107	53,682
Vested (in shares)	(59,803)	(7,017)
Forfeited (in shares)	(93)	(5,073)
Canceled (in shares)	0	0
Shares, end of period (in shares)	185,407	175,196
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)	$ 36.29	$ 33.39
Granted (in dollars per share)	28.55	29.52
Vested (in dollars per share)	30.78	18
Forfeited (in dollars per share)	37.72	37.75
Canceled (in dollars per share)	0	0
Shares, end of period (in dollars per share)	38.50	36.29
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	Mar. 31, 2019	Sep. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$ 1,763,305	$ 1,385,650
Fair value loans	835,822	865,386
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	93,819	167,172
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,605,616	1,149,707
States and political subdivision securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	62,870	67,775
Fair value, measurements, recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,763,305	1,385,650
Derivatives-assets	25,843	1,911
Derivatives-liabilities	58	2,188
Fair value loans	835,822	865,386
Loan servicing rights	2,674	3,087
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	93,819	167,172
Fair value, measurements, recurring | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,605,616	1,149,707
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	62,870	67,775
Fair value, measurements, recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,000	996
Fair value, measurements, recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	93,819	167,172
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	93,819	167,172
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	1,668,175	1,217,508
Derivatives-assets	25,843	1,911
Derivatives-liabilities	58	2,188
Fair value loans	835,822	865,386
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 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,605,616	1,149,707
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	61,559	66,805
Fair value, measurements, recurring | Level 2 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,000	996
Fair value, measurements, recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,311	970
Derivatives-assets	0	0
Derivatives-liabilities	0	0
Fair value loans	0	0
Loan servicing rights	2,674	3,087
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 | 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	1,311	970
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		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 961	$ 965	$ 970	$ 1,069
Additions	350	0	350	0
Principal paydown	0	0	(9)	(104)
Balance, end of period	1,311	965	1,311	965
Loan servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,862	3,799	3,087	4,074
Realized and unrealized (loss)	(188)	(213)	(413)	(488)
Balance, end of period	$ 2,674	$ 3,586	$ 2,674	$ 3,586

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	Mar. 31, 2019	Sep. 30, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	$ 31,834	$ 22,225
Impaired loans	200,312	188,017
Loans held for sale, at lower of cost or fair value	3,648	5,456
Property held for sale	3,216	1,104
Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	0	0
Impaired loans	0	0
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
Loans held for sale, at lower of cost or fair value	3,648	5,456
Property held for sale	0	0
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other repossessed property	31,834	22,225
Impaired loans	200,312	188,017
Loans held for sale, at lower of cost or fair value	0	0
Property held for sale	$ 3,216	$ 1,104

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	Mar. 31, 2019	Sep. 30, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Property held for sale	$ 3,216	$ 1,104
Fair value, measurements, nonrecurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	31,834	22,225
Impaired loans	200,312	188,017
Fair value, measurements, nonrecurring | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	31,834	22,225
Impaired loans	200,312	$ 188,017
Property held for sale	$ 3,216

Fair Value Measurements - Sch_3

Fair Value Measurements - Schedule of Fair Values for Balance Sheet Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Liabilities
Unamortized discount on acquired loans	$ 13,500	$ 13,000
Level 1 | Carrying Amount
Assets
Cash and cash equivalents	282,638	298,696
Level 1 | Fair Value
Assets
Cash and cash equivalents	282,638	298,696
Level 3 | Carrying Amount
Assets
Loans, net, excluding fair valued loans, loans held for sale and impaired loans ¹	8,731,128	8,357,065
Level 3 | Fair Value
Assets
Loans, net, excluding fair valued loans, loans held for sale and impaired loans ¹	8,721,910	8,231,829
Level 2 | Carrying Amount
Liabilities
Time deposits	2,087,558	1,847,078
FHLB advances and other borrowings	275,000	275,000
Securities sold under repurchase agreements	62,537	90,907
Subordinated debentures and subordinated notes payable	108,528	108,468
Level 2 | Fair Value
Liabilities
Time deposits	2,086,538	1,848,550
FHLB advances and other borrowings	280,374	275,797
Securities sold under repurchase agreements	62,537	90,907
Subordinated debentures and subordinated notes payable	$ 102,285	$ 107,841

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			6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 44,511	$ 40,532	$ 40,532	$ 90,297	$ 69,762
Weighted average common shares outstanding (in shares)	56,994,817	58,941,315		57,484,838	58,921,972
Dilutive effect of stock based compensation (in shares)	79,857	204,802		72,146	194,951
Weighted average common shares outstanding for diluted earnings per share calculation (in shares)	57,074,674	59,146,117		57,556,984	59,116,923
Basic earnings per share (in dollars per share)	$ 0.78	$ 0.69		$ 1.57	$ 1.18
Diluted earnings per share (in dollars per share)	$ 0.78	$ 0.69		$ 1.57	$ 1.18

Earnings per Share - Narrative

Earnings per Share - Narrative (Details) - shares	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Performance shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share (in shares)	0	0
Stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of earnings per share (in shares)	67,971	0