Business Combinations - Information about Loans Acquired (Detail) - USD ($) $ in Thousands	Nov. 10, 2022	Oct. 01, 2021
Business Acquisition [Line Items]
Fair value of acquired loans	$ 26
American State Bank Trust Company [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		$ 441,884
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		327,169
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		97,554
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		62,901
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		37,766
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		57,158
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		55,971
American State Bank Trust Company [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		15,819
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		114,715
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		91,137
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		1,950
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		2,251
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		9,763
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		9,432
American State Bank Trust Company [Member] | Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		182
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		330,644
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		98,774
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		63,249
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		37,919
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		58,632
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		56,238
American State Bank Trust Company [Member] | Loan Par Value [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		15,832
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		122,031
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		95,812
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		2,017
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		2,842
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		10,424
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		10,693
American State Bank Trust Company [Member] | Loan Par Value [Member] | Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		243
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(5,612)
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(3,719)
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(60)
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(244)
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(421)
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(1,113)
American State Bank Trust Company [Member] | Credit Marks in ACL [Member] | Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(55)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(3,475)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(1,220)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(348)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(153)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(1,474)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(267)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Non-Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(13)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(1,704)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(956)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member] | Commercial and Industrial [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(7)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member] | Residential Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(347)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural Real Estate [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(240)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member] | Agricultural [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		(148)
American State Bank Trust Company [Member] | Fair Value Marks [Member] | Purchase Credit Deteriorated Loans [Member] | Consumer [Member]
Business Acquisition [Line Items]
Fair value of acquired loans		$ (6)