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Regulatory Capital - Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Total risk-based capital: |  |
Actual amount | $ 1,575.7 | $ 1,495.3
Capital to Risk Weighted Assets | 14.19% | 14.10%
Adequately capitalized Basel III phase-in schedule, amount | $ 888.3 | $ 848.5
Adequately capitalized Basel III phase-in schedule, ratio (percent) | 8.00% | 8.00%
Adequately capitalized Basel III fully phased-in, amount | $ 1,165.8 | $ 1,113.6
Capital Required For Capital Adequacy Under Basel III Fully Phased-In To Risk Weighted Assets | 10.50% | 10.50%
Well capitalized, amount | $ 1,110.3 | $ 1,060.6
Capital Required to be Well Capitalized to Risk Weighted Assets | 10.00% | 10.00%
Tier 1 risk-based capital: |  |
Actual amount | $ 1,369.0 | $ 1,422.3
Tier One Risk Based Capital to Risk Weighted Assets | 12.33% | 13.41%
Adequately capitalized Basel III phase-in schedule, amount | $ 666.2 | $ 636.3
Adequately capitalized Basel III phase-in schedule, ratio (percent) | 6.00% | 6.00%
Adequately capitalized Basel III fully phased-in, amount | $ 943.8 | $ 901.5
Tier One Capital Required For Capital Adequacy Under Basel III Fully Phased-In To Risk Weighted Assets | 8.50% | 8.50%
Well capitalized, amount | $ 888.3 | $ 848.5
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets | 8.00% | 8.00%
Common Equity Tier One Capital [Abstract] |  |
Actual amount | $ 1,284.9 | $ 1,338.2
Common Equity Tier One Risk Based Capital To Risk Weighted Assets | 11.57% | 12.62%
Adequately capitalized Basel III phase-in schedule, amount | $ 499.6 | $ 477.3
Adequately capitalized Basel III phase-in schedule, ratio (percent) | 4.50% | 4.50%
Adequately capitalized Basel III fully phased-in, amount | $ 777.2 | $ 742.4
Tier One Common Equity Capital Required For Capital Adequacy Under Basel III Fully Phased-In To Risk Weighted Assets | 7.00% | 7.00%
Well capitalized, amount | $ 721.7 | $ 689.4
Common Equity Tier One Capital To Be Well Capitalized To Risk Weighted Assets | 6.50% | 6.50%
Leverage capital ratio: |  |
Actual amount | $ 1,369.0 | $ 1,422.3
Tier One Leverage Capital to Average Assets | 8.16% | 10.13%
Adequately capitalized, amount | $ 671.0 | $ 561.6
Adequately capitalized, ratio (percent) | 4.00% | 4.00%
Well capitalized, amount | $ 838.7 | $ 702.0
Well capitalized, ratio (percent) | 5.00% | 5.00%
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | $ (24.1) |
Retained Earnings [Member] |  |
Leverage capital ratio: |  |
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification | (24.1) |
FIB |  |
Total risk-based capital: |  |
Actual amount | $ 1,426.8 | $ 1,321.4
Capital to Risk Weighted Assets | 12.89% | 12.50%
Adequately capitalized Basel III phase-in schedule, amount | $ 885.6 | $ 845.8
Adequately capitalized Basel III phase-in schedule, ratio (percent) | 8.00% | 8.00%
Adequately capitalized Basel III fully phased-in, amount | $ 1,162.3 | $ 1,110.1
Capital Required For Capital Adequacy Under Basel III Fully Phased-In To Risk Weighted Assets | 10.50% | 10.50%
Well capitalized, amount | $ 1,107.0 | $ 1,057.2
Capital Required to be Well Capitalized to Risk Weighted Assets | 10.00% | 10.00%
Tier 1 risk-based capital: |  |
Actual amount | $ 1,320.1 | $ 1,248.4
Tier One Risk Based Capital to Risk Weighted Assets | 11.93% | 11.81%
Adequately capitalized Basel III phase-in schedule, amount | $ 664.2 | $ 634.3
Adequately capitalized Basel III phase-in schedule, ratio (percent) | 6.00% | 6.00%
Adequately capitalized Basel III fully phased-in, amount | $ 940.9 | $ 898.6
Tier One Capital Required For Capital Adequacy Under Basel III Fully Phased-In To Risk Weighted Assets | 8.50% | 8.50%
Well capitalized, amount | $ 885.6 | $ 845.8
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets | 8.00% | 8.00%
Common Equity Tier One Capital [Abstract] |  |
Actual amount | $ 1,320.1 | $ 1,248.4
Common Equity Tier One Risk Based Capital To Risk Weighted Assets | 11.93% | 11.81%
Adequately capitalized Basel III phase-in schedule, amount | $ 498.1 | $ 475.7
Adequately capitalized Basel III phase-in schedule, ratio (percent) | 4.50% | 4.50%
Adequately capitalized Basel III fully phased-in, amount | $ 774.9 | $ 740.0
Tier One Common Equity Capital Required For Capital Adequacy Under Basel III Fully Phased-In To Risk Weighted Assets | 7.00% | 7.00%
Well capitalized, amount | $ 719.5 | $ 687.2
Common Equity Tier One Capital To Be Well Capitalized To Risk Weighted Assets | 6.50% | 6.50%
Leverage capital ratio: |  |
Actual amount | $ 1,320.1 | $ 1,248.4
Tier One Leverage Capital to Average Assets | 7.88% | 8.91%
Adequately capitalized, amount | $ 669.7 | $ 560.4
Adequately capitalized, ratio (percent) | 4.00% | 4.00%
Well capitalized, amount | $ 837.2 | $ 700.4
Well capitalized, ratio (percent) | 5.00% | 5.00%

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