v3.26.3
ACQUISITION AND DIVESTITURE ACTIVITY - Schedule of Assets Acquired and Liabilities Assumed and the Fair Value of Consideration (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended
May 01, 2025
Jun. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Jun. 30, 2026
Dec. 31, 2025
Dec. 31, 2024
Assets              
Goodwill   $ 2,409,886 $ 2,429,756 $ 2,418,658 $ 2,429,756 $ 2,425,700 $ 2,175,251
Liabilities              
Securities sold under agreements to repurchase     240,698 277,594   $ 261,366  
Fair value of consideration              
Common stock (50,183 shares issued at $20.59 per share)   1,033,262 $ 0 $ 1,033,262      
Common Stock              
Fair value of consideration              
Common stock (50,183 shares issued at $20.59 per share)   $ 50,183          
Bremer              
Assets              
Cash and cash equivalents $ 449,757            
Equity securities 26,070            
Investment securities 2,811,108            
FHLB/Federal Reserve Bank stock 93,924            
Loans held-for-sale 9,883            
Loans, net of allowance for credit losses 11,110,423            
Premises and equipment 99,965            
Goodwill 254,505            
Other intangible assets 440,099            
Company-owned life insurance 181,909            
Other assets 793,404            
Total assets 16,271,047            
Liabilities              
Deposits 12,862,357            
Securities sold under agreements to repurchase 49,131            
Federal Home Loan Bank advances 1,559,227            
Other borrowings 205,194            
Accrued expenses and other liabilities 247,243            
Total liabilities 14,923,152            
Fair value of consideration              
Cash 314,633            
Total consideration 1,347,895            
Bremer | Common Stock              
Fair value of consideration              
Common stock (50,183 shares issued at $20.59 per share) $ 1,033,262            
Issuance of common stock shares for acquisitions of business (in shares) 50,183,000            
Share price (in dollars per share) $ 20.59