Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Total	Blackhawk Bancorp, Inc	Common Stock	Common Stock Blackhawk Bancorp, Inc	Additional Paid-in Capital	Additional Paid-in Capital Blackhawk Bancorp, Inc	Retained Earnings	Deferred Compensation	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance at Dec. 31, 2022	$ 633,155,000		$ 86,366,000		$ 427,001,000		$ 289,284,000	$ 2,064,000	$ (151,507,000)	$ (20,053,000)
Net Income (Loss)	68,935,000						68,935,000
Other comprehensive income (loss), net of tax	15,080,000								15,080,000
Dividends on common stock	(19,557,000)						(19,557,000)
Issuance of restricted shares pursuant to 2017 stock incentive plan, net of forfeitures	1,620,000		218,000		1,402,000
Issuance of common shares pursuant to the 2017 stock incentive plan, net of forfeitures	127,000		18,000		109,000
Issuance of shares pursuant to the acquisition		$ 93,508,000		$ 13,161,000		$ 80,347,000
Issuance of common shares pursuant to the employee stock purchase plan	877,000		156,000		721,000
Purchase of treasury shares	(465,000)									(465,000)
Deferred compensation	(1,140,000)							(765,000)		(375,000)
Grant of restricted stock units pursuant to the 2017 stock incentive plan	1,048,000				1,048,000
Release of restricted stock units pursuant to the 2017 stock incentive plan	(1,529,000)				(1,529,000)
Vested restricted shares/units compensation expense	1,545,000				215,000			1,330,000
Ending Balance at Dec. 31, 2023	793,204,000		99,919,000		509,314,000		338,662,000	2,629,000	(136,427,000)	(20,893,000)
Net Income (Loss)	78,898,000						78,898,000
Other comprehensive income (loss), net of tax	(5,956,000)								(5,956,000)
Dividends on common stock	(22,371,000)						(22,371,000)
Issuance of restricted shares pursuant to 2017 stock incentive plan, net of forfeitures	1,542,000		184,000		1,358,000
Issuance of common shares pursuant to the 2017 stock incentive plan, net of forfeitures	192,000		23,000		169,000
Issuance of shares pursuant to the acquisition				$ 0		$ 0
Issuance of common shares pursuant to the employee stock purchase plan	862,000		132,000		730,000
Purchase of treasury shares	(659,000)									(659,000)
Deferred compensation	(2,526,000)							(1,839,000)		(687,000)
Grant of restricted stock units pursuant to the 2017 stock incentive plan	1,634,000				1,634,000
Release of restricted stock units pursuant to the 2017 stock incentive plan	(617,000)				(617,000)
Vested restricted shares/units compensation expense	2,188,000				222,000			1,966,000
Ending Balance at Dec. 31, 2024	846,391,000		100,258,000		512,810,000		395,189,000	2,756,000	(142,383,000)	(22,239,000)
Net Income (Loss)	91,749,000						91,749,000
Other comprehensive income (loss), net of tax	41,082,000								41,082,000
Dividends on common stock	(23,395,000)						(23,395,000)
Issuance of restricted shares pursuant to 2017 stock incentive plan, net of forfeitures	2,831,000		290,000		2,541,000
Issuance of common shares pursuant to the 2017 stock incentive plan, net of forfeitures	223,000		23,000		200,000
Issuance of common shares pursuant to the employee stock purchase plan	897,000		117,000		780,000
Purchase of treasury shares	(724,000)									(724,000)
Deferred compensation	(3,201,000)							(2,288,000)		(913,000)
Grant of restricted stock units pursuant to the 2017 stock incentive plan	2,070,000				2,070,000
Release of restricted stock units pursuant to the 2017 stock incentive plan	(1,634,000)				(1,634,000)
Vested restricted shares/units compensation expense	2,403,000				217,000			2,186,000
Ending Balance at Dec. 31, 2025	$ 958,692,000		$ 100,688,000		$ 516,984,000		$ 463,543,000	$ 2,654,000	$ (101,301,000)	$ (23,876,000)