v3.25.2
Fair Value Measurements - Schedule of Estimated Fair Values of Financial Instruments by Level of Valuation Inputs (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Estimated Fair Value    
Financial assets:    
Cash and cash equivalents $ 1,090.2 $ 896.6
Investment debt securities held-to-maturity 2,317.0 2,358.6
Accrued interest receivable 105.7 116.8
Mortgage servicing rights, net 35.7 35.4
Net loans held for investment 15,750.4 17,154.7
Total financial assets 19,299.0 20,562.1
Financial liabilities:    
Time deposits 2,782.0 2,875.5
Securities sold under repurchase agreements 509.3 523.9
Other Borrowings 250.0 1,567.5
Accrued interest payable 41.3 47.0
Long-term debt 256.7 131.9
Subordinated debentures held by subsidiary trusts 149.5 152.3
Total financial liabilities 23,822.8 25,423.2
Deposits, Excluding Time Deposits, Fair Value Disclosure 19,834.0 20,125.1
Carrying Amount    
Financial assets:    
Cash and cash equivalents 1,090.2 896.6
Investment debt securities held-to-maturity 2,570.0 2,687.5
Accrued interest receivable 105.7 116.8
Mortgage servicing rights, net 24.4 25.7
Net loans held for investment 16,143.8 17,640.8
Total financial assets 19,934.1 21,367.4
Financial liabilities:    
Time deposits 2,796.6 2,890.5
Securities sold under repurchase agreements 509.3 523.9
Other Borrowings 250.0 1,567.5
Accrued interest payable 41.3 47.0
Long-term debt 252.0 132.2
Subordinated debentures held by subsidiary trusts 163.1 163.1
Total financial liabilities 23,846.3 25,449.3
Deposits, Excluding Time Deposits, Fair Value Disclosure 19,834.0 20,125.1
Investment debt securities held-to-maturity 2,317.0 2,358.6
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value    
Financial assets:    
Cash and cash equivalents 1,090.2 896.6
Investment debt securities held-to-maturity 0.0 0.0
Accrued interest receivable 0.0 0.0
Mortgage servicing rights, net 0.0 0.0
Net loans held for investment 0.0 0.0
Total financial assets 1,090.2 896.6
Financial liabilities:    
Time deposits 0.0 0.0
Securities sold under repurchase agreements 0.0 0.0
Other Borrowings 0.0 0.0
Accrued interest payable 0.0 0.0
Long-term debt 0.0 0.0
Subordinated debentures held by subsidiary trusts 0.0 0.0
Total financial liabilities 19,834.0 20,125.1
Deposits, Excluding Time Deposits, Fair Value Disclosure 19,834.0 20,125.1
Significant Other Observable Inputs (Level 2) | Estimated Fair Value    
Financial assets:    
Cash and cash equivalents 0.0 0.0
Investment debt securities held-to-maturity 2,317.0 2,358.6
Accrued interest receivable 105.7 116.8
Mortgage servicing rights, net 35.7 35.4
Net loans held for investment 0.0 0.0
Total financial assets 2,458.4 2,510.8
Financial liabilities:    
Time deposits 2,782.0 2,875.5
Securities sold under repurchase agreements 509.3 523.9
Other Borrowings 250.0 1,567.5
Accrued interest payable 41.3 47.0
Long-term debt 256.7 131.9
Subordinated debentures held by subsidiary trusts 149.5 152.3
Total financial liabilities 3,988.8 5,298.1
Deposits, Excluding Time Deposits, Fair Value Disclosure 0.0 0.0
Significant Unobservable Inputs (Level 3) | Estimated Fair Value    
Financial assets:    
Cash and cash equivalents 0.0 0.0
Investment debt securities held-to-maturity 0.0 0.0
Accrued interest receivable 0.0 0.0
Mortgage servicing rights, net 0.0 0.0
Net loans held for investment 15,750.4 17,154.7
Total financial assets 15,750.4 17,154.7
Financial liabilities:    
Time deposits 0.0 0.0
Securities sold under repurchase agreements 0.0 0.0
Other Borrowings 0.0 0.0
Accrued interest payable 0.0 0.0
Long-term debt 0.0 0.0
Subordinated debentures held by subsidiary trusts 0.0 0.0
Total financial liabilities 0.0 0.0
Deposits, Excluding Time Deposits, Fair Value Disclosure $ 0.0 $ 0.0