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Fair Value Measurements - Schedule of Estimated Fair Values of Financial Instruments by Level of Valuation Inputs (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Financial assets: |  |
Estimated Fair Value | $ 6,946.1 | $ 4,820.5
Held-to-maturity investment securities, estimated fair value | 3,052.2 | 1,667.5
Derivative assets | 45.2 | 28.1
Deferred compensation plan assets | 18.7 | 21.4
Financial liabilities: |  |
Derivative liabilities | 159.6 | 18.2
Deferred compensation plan liabilities | 18.7 | 21.4
Carrying Amount |  |
Financial assets: |  |
Cash and cash equivalents | 870.5 | 2,344.8
Estimated Fair Value | 6,946.1 | 4,820.5
Held-to-maturity investment securities, estimated fair value | 3,451.8 | 1,687.6
Accrued interest receivable | 118.3 | 47.4
Mortgage servicing rights, net | 31.1 | 28.2
Loans Held-for-sale, Fair Value Disclosure | 79.9 | 30.1
Net loans held for investment | 17,879.1 | 9,209.4
Derivative assets | 45.2 | 28.1
Deferred compensation plan assets | 18.7 | 21.4
Total financial assets | 29,440.7 | 18,217.5
Financial liabilities: |  |
Total deposits, excluding time deposits | 23,145.2 | 15,303.1
Time deposits | 1,928.4 | 966.5
Securities sold under repurchase agreements | 1,052.9 | 1,051.1
Federal Home Loan Bank Borrowings, Fair Value Disclosure | 2,327.0 |
Accrued interest payable | 14.5 | 3.7
Long-term debt | 120.8 | 112.4
Subordinated debentures held by subsidiary trusts | 163.1 | 87.0
Derivative liabilities | 159.6 | 18.2
Deferred compensation plan liabilities | 18.7 | 21.4
Total financial liabilities | 28,930.2 | 17,563.4
Estimated Fair Value |  |
Financial assets: |  |
Cash and cash equivalents | 870.5 | 2,344.8
Estimated Fair Value | 6,946.1 | 4,820.5
Held-to-maturity investment securities, estimated fair value | 3,052.2 | 1,667.5
Accrued interest receivable | 118.3 | 47.4
Mortgage servicing rights, net | 37.4 | 28.2
Loans Held-for-sale, Fair Value Disclosure | 79.9 | 30.1
Net loans held for investment | 17,552.1 | 9,254.3
Derivative assets | 45.2 | 28.1
Deferred compensation plan assets | 18.7 | 21.4
Total financial assets | 28,720.4 | 18,242.3
Financial liabilities: |  |
Total deposits, excluding time deposits | 23,145.2 | 15,303.1
Time deposits | 1,876.1 | 963.1
Securities sold under repurchase agreements | 1,052.9 | 1,051.1
Federal Home Loan Bank Borrowings, Fair Value Disclosure | 2,327.0 |
Accrued interest payable | 14.5 | 3.7
Long-term debt | 116.3 | 120.7
Subordinated debentures held by subsidiary trusts | 155.8 | 85.5
Derivative liabilities | 159.6 | 18.2
Deferred compensation plan liabilities | 18.7 | 21.4
Total financial liabilities | 28,866.1 | 17,566.8
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value |  |
Financial assets: |  |
Cash and cash equivalents | 870.5 | 2,344.8
Estimated Fair Value | 0.0 | 684.7
Held-to-maturity investment securities, estimated fair value | 0.0 | 0.0
Accrued interest receivable | 0.0 | 0.0
Mortgage servicing rights, net | 0.0 | 0.0
Loans Held-for-sale, Fair Value Disclosure | 0.0 | 0.0
Net loans held for investment | 0.0 | 0.0
Derivative assets | 0.0 | 0.0
Deferred compensation plan assets | 0.0 | 0.0
Total financial assets | 870.5 | 3,029.5
Financial liabilities: |  |
Total deposits, excluding time deposits | 23,145.2 | 15,303.1
Time deposits | 0.0 | 0.0
Securities sold under repurchase agreements | 0.0 | 0.0
Federal Home Loan Bank Borrowings, Fair Value Disclosure | 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
Derivative liabilities | 0.0 | 0.0
Deferred compensation plan liabilities | 0.0 | 0.0
Total financial liabilities | 23,145.2 | 15,303.1
Significant Other Observable Inputs (Level 2) | Estimated Fair Value |  |
Financial assets: |  |
Cash and cash equivalents | 0.0 | 0.0
Estimated Fair Value | 6,946.1 | 4,135.8
Held-to-maturity investment securities, estimated fair value | 3,052.2 | 1,667.5
Accrued interest receivable | 118.3 | 47.4
Mortgage servicing rights, net | 37.4 | 28.2
Loans Held-for-sale, Fair Value Disclosure | 79.9 | 30.1
Net loans held for investment | 17,513.0 | 9,242.6
Derivative assets | 45.2 | 28.1
Deferred compensation plan assets | 18.7 | 21.4
Total financial assets | 27,810.8 | 15,201.1
Financial liabilities: |  |
Total deposits, excluding time deposits | 0.0 | 0.0
Time deposits | 1,876.1 | 963.1
Securities sold under repurchase agreements | 1,052.9 | 1,051.1
Federal Home Loan Bank Borrowings, Fair Value Disclosure | 2,327.0 |
Accrued interest payable | 14.5 | 3.7
Long-term debt | 116.3 | 120.7
Subordinated debentures held by subsidiary trusts | 155.8 | 85.5
Derivative liabilities | 159.6 | 18.2
Deferred compensation plan liabilities | 18.7 | 21.4
Total financial liabilities | 5,720.9 | 2,263.7
Significant Unobservable Inputs (Level 3) | Estimated Fair Value |  |
Financial assets: |  |
Cash and cash equivalents | 0.0 | 0.0
Estimated Fair Value | 0.0 | 0.0
Held-to-maturity investment securities, estimated fair value | 0.0 | 0.0
Accrued interest receivable | 0.0 | 0.0
Mortgage servicing rights, net | 0.0 | 0.0
Loans Held-for-sale, Fair Value Disclosure | 0.0 | 0.0
Net loans held for investment | 39.1 | 11.7
Derivative assets | 0.0 | 0.0
Deferred compensation plan assets | 0.0 | 0.0
Total financial assets | 39.1 | 11.7
Financial liabilities: |  |
Total deposits, excluding time deposits | 0.0 | 0.0
Time deposits | 0.0 | 0.0
Securities sold under repurchase agreements | 0.0 | 0.0
Federal Home Loan Bank Borrowings, Fair Value Disclosure | 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
Derivative liabilities | 0.0 | 0.0
Deferred compensation plan liabilities | 0.0 | 0.0
Total financial liabilities | $ 0.0 | $ 0.0

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