v3.26.1
Acquisition - Additional Information (Detail)
$ / shares in Units, shares in Thousands, $ in Thousands
3 Months Ended 6 Months Ended
Jan. 31, 2025
USD ($)
$ / shares
shares
Jun. 30, 2026
USD ($)
$ / shares
shares
Sep. 30, 2025
USD ($)
Jun. 30, 2025
USD ($)
$ / shares
Jun. 30, 2026
USD ($)
$ / shares
shares
Jun. 30, 2025
USD ($)
$ / shares
Jan. 01, 2026
USD ($)
Dec. 31, 2025
USD ($)
shares
Dec. 31, 2024
USD ($)
Business Combination [Line Items]                  
Preferred stock, shares issued | shares   30     30     30  
Goodwill   $ 1,837,594     $ 1,837,594     $ 1,839,825 $ 207,385
Fair value of PCD Loans $ 3,046,521                
Fair value of Non-PCD 9,734,711                
Unpaid Principal Balance 10,304,570                
Long-term debt   480,126     480,126     474,229  
Net income available to common shareholders   $ 271,758   $ 215,382 $ 527,383 $ 294,702      
Basic earnings per share | $ / shares   $ 3.58   $ 2.84 $ 6.94 $ 4.18      
PCD ACL at acquisition 85,299     $ 15,167   $ 77,293      
Non-PCD                  
Business Combination [Line Items]                  
Fair value of Non-PCD 6,688,190                
Unpaid Principal Balance $ 7,067,238                
Commercial Banking [Member]                  
Business Combination [Line Items]                  
Goodwill   $ 1,041,238     $ 1,041,238     1,042,577 63,113
Personal Banking [Member]                  
Business Combination [Line Items]                  
Goodwill   $ 719,864     719,864     $ 720,756 $ 67,780
Preferred Stock [Member]                  
Business Combination [Line Items]                  
Business combination, consideration shares value           115,230      
Common Stock [Member]                  
Business Combination [Line Items]                  
Business combination, consideration shares value           $ 2,783,510      
Heartland Financial USA Inc [Member]                  
Business Combination [Line Items]                  
Acquisition date Jan. 31, 2025                
Business acquisition, all-stock transaction shares issued | shares 23,600                
Preferred stock, shares issued | shares 4,600                
Date of merger Apr. 28, 2024                
Business combination, consideration shares value $ 2,919,129                
Business acquisition exchange ratio on common stock 0.55                
Tax deductible goodwill $ 44,000                
Goodwill 1,630,209                
Identifiable intangible assets 511,021                
Loans acquired from HTLF 9,734,711                
Fair value of PCD Loans 3,000,000                
Core deposit intangible asset 474,100                
Customer lists 26,000                
Purchased credit card relationships 10,900                
Business acquisition transaction costs 140,100                
Provision expense related to acquisition 62,000                
Net assets acquired 2,919,129                
PCD ACL at acquisition     $ 8,000 $ 15,200 $ 62,100        
Valuation allowance             $ 2,200    
Heartland Financial USA Inc [Member] | Subordinated notes 2.75% [Member]                  
Business Combination [Line Items]                  
Subordinated notes, issued $ 150,000                
Debt instrument, interest rate 2.75%                
Fair value of subordinated notes $ 138,800                
Maturity Date Sep. 15, 2031                
Heartland Financial USA Inc [Member] | Trust Preferred Securities [Member]                  
Business Combination [Line Items]                  
Long-term debt $ 159,800                
Long-term debt, fair value $ 139,300                
Heartland Financial USA Inc [Member] | Trust Preferred Securities [Member] | Maximum [Member]                  
Business Combination [Line Items]                  
Interest rates 8.21%                
Maturity Date         Sep. 30, 2037        
Heartland Financial USA Inc [Member] | Trust Preferred Securities [Member] | Minimum [Member]                  
Business Combination [Line Items]                  
Interest rates 5.89%                
Maturity Date         Sep. 30, 2032        
Heartland Financial USA Inc [Member] | Commercial Banking [Member]                  
Business Combination [Line Items]                  
Goodwill $ 978,100                
Heartland Financial USA Inc [Member] | Personal Banking [Member]                  
Business Combination [Line Items]                  
Goodwill $ 652,100                
Heartland Financial USA Inc [Member] | Preferred Stock [Member]                  
Business Combination [Line Items]                  
Preferred stock, fixed rate percentage 7.00%                
Business combination, consideration shares value $ 115,230                
Business acquisition, share price | $ / shares $ 25.05                
Heartland Financial USA Inc [Member] | Common Stock [Member]                  
Business Combination [Line Items]                  
Business combination, consideration shares value $ 2,783,510                
Business acquisition, share price | $ / shares $ 117.9