Loans and Leases and Allowance for Credit Losses - Activity in Allowance for Loan and Lease Losses, before ASU 2016-13 Adoption (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually, before ASU 2016-13 adoption		$ 12,296
Collectively, before ASU 2016-13 adoption		2,127,530
Total Financing Receivables, before ASU 2016-13 adoption	$ 1,987,861	2,139,826
Commercial, Residential, and Farm Land Real Estate Portfolio Segment [Member] \| Real Estate Sector [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually, before ASU 2016-13 adoption		10,150
Collectively, before ASU 2016-13 adoption		1,822,774
Total Financing Receivables, before ASU 2016-13 adoption		1,832,924
Agricultural Portfolio Segment [Member] \| Agricultural Sector [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually, before ASU 2016-13 adoption		471
Collectively, before ASU 2016-13 adoption		42,825
Total Financing Receivables, before ASU 2016-13 adoption		43,296
Commercial Portfolio Segment [Member] \| Commercial and Industrial Sector [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually, before ASU 2016-13 adoption		1,512
Collectively, before ASU 2016-13 adoption		257,266
Total Financing Receivables, before ASU 2016-13 adoption		258,778
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Individually, before ASU 2016-13 adoption		163
Collectively, before ASU 2016-13 adoption		4,665
Total Financing Receivables, before ASU 2016-13 adoption		$ 4,828

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

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- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

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- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

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