Goodwill and Intangible Assets - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 20, 2023	Dec. 31, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2025	Dec. 31, 2024	Sep. 30, 2023	Jun. 30, 2023
Finite Lived Intangible Assets [Line Items]
Intangible assets amortization period		15 years			15 years
Goodwill, net		$ 203,391,000			$ 203,391,000	$ 203,391,000
Principal balance of mortgage loans serviced for others		$ 509,700,000			$ 509,700,000	$ 572,600,000
Weighted average amortization period of intangibles					3 years 5 months 8 days
Core Deposit Intangibles
Finite Lived Intangible Assets [Line Items]
Intangible assets amortization period		10 years			10 years
Weighted average amortization period of intangibles					2 years 10 months 28 days
Customer List Intangibles
Finite Lived Intangible Assets [Line Items]
Weighted average amortization period of intangibles					4 years 2 months 19 days
Maximum | Customer List Intangibles
Finite Lived Intangible Assets [Line Items]
Intangible assets amortization period		12 years			12 years
Minimum | Customer List Intangibles
Finite Lived Intangible Assets [Line Items]
Intangible assets amortization period		3 years			3 years
Mid Rivers
Finite Lived Intangible Assets [Line Items]
Goodwill acquired during period				$ 6,900,000
Goodwill, net				$ 6,930,000
Blackhawk Bancorp, Inc
Finite Lived Intangible Assets [Line Items]
Goodwill acquired during period	$ 50,100,000
Goodwill, net							$ 50,097,000
Blackhawk Bancorp, Inc | Core Deposit Intangibles
Finite Lived Intangible Assets [Line Items]
Intangible assets amortization period	10 years
Purdum, Gray, Ingledue, Beck, Inc.
Finite Lived Intangible Assets [Line Items]
Goodwill, net								$ 5,951,000
AAdvantage Insurance Group LLC's | Customer List Intangibles
Finite Lived Intangible Assets [Line Items]
Intangible assets acquired			$ 2,800,000
Ray Farm Management Services, Inc's | Customer List Intangibles
Finite Lived Intangible Assets [Line Items]
Intangible assets acquired		$ 764,000