v3.26.1
LONG-TERM DEBT AND SHAREHOLDERS' EQUITY (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 8 Months Ended 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2026
Dec. 31, 2025
Jan. 31, 2026
Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Preferred stock, shares authorized (in shares) 4,400,000     4,400,000    
Preferred stock, liquidation preference (in dollars per share) $ 1,000          
Common stock, outstanding shares (in shares) 147,077,000     147,653,000    
Common stock, par value (in dollars per share) $ 0.001     $ 0.001    
Common stock and additional paid in capital $ 1,669.0     $ 1,726.0    
Accumulated other comprehensive loss 7,296.0 $ 6,327.0   7,180.0   $ 6,124.0
Unrealized loss amortization associated with the securities transferred from AFS to HTM $ 40.0 43.0        
Share repurchase program, authorized amount         $ 75.0  
Common stock repurchased (in shares) 1,300,000          
Shares repurchased $ 77.0 41.0        
Shares repurchased (in dollars per share) $ 60.79          
Accumulated other comprehensive income (loss)            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Accumulated other comprehensive loss $ (1,935.0) $ (2,250.0)   (1,941.0)   $ (2,380.0)
Stock Compensation Plan            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Shares repurchased $ 2.0          
Series A Preferred Stock            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Preferred stock outstanding (in shares) 66,139          
Fixed-Rate Available For Sale Securities            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Unrealized loss amortization associated with the securities transferred from AFS to HTM, before tax $ 1,500.0     1,600.0    
Unrealized loss amortization associated with the securities transferred from AFS to HTM 1,200.0     $ 1,200.0    
Forecast            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Shares repurchased     $ 225.0      
4.48% Fixed-To-Floating Senior Notes | Senior notes            
Accumulated Other Comprehensive Income (Loss) [Line Items]            
Debt instrument face amount $ 500.0          
Debt instrument stated interest rate 4.48%