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Regulatory Capital - Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) - USD ($) $ in Millions | Jun. 30, 2018 | Dec. 31, 2017
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Total risk-based capital: |  |
Actual Amount | $ 1,160.9 | $ 1,112.5
Actual Ratio | 12.97488% | 12.75962%
Capital Required for Capital Adequacy under Basel III Phase-in Schedule | $ 883.6 | $ 806.5
Capital Required for Capital Adequacy under Basel III Phase-in Schedule to Risk Weighted Assets | 9.875% | 9.25%
Capital Required for Capital Adequacy under Basel III Fully Phased-in | $ 939.5 | $ 915.5
Capital Required for Capital Adequacy under Basel III Fully Phased-in to Risk Weighted Assets | 10.50% | 10.50%
Well Capitalized Amount | $ 894.7 | $ 871.9
Well Capitalized Ratio | 10.00% | 10.00%
Tier 1 risk-based capital: |  |
Actual Amount | $ 1,086.8 | $ 1,040.3
Actual Ratio | 12.14683% | 11.93154%
Tier One Risk Based Capital under Basel III Phase-in Schedule | $ 704.6 | $ 632.1
Tier One Capital Required for Capital Adequacy under Basel III Phase-in Schedule to Risk Weighted Assets | 7.875% | 7.25%
Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in | $ 760.5 | $ 741.1
Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in to Risk Weighted Assets | 8.50% | 8.50%
Well Capitalized Amount | $ 715.8 | $ 697.5
Well Capitalized Ratio | 8.00% | 8.00%
Common equity tier one risk-based capital: |  |
Actual Amount | $ 1,006.8 | $ 962.4
Actual Ratio | 11.25272% | 11.03808%
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Phase-in Schedule | $ 570.4 | $ 501.3
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Phase-in Schedule to Risk Weighted Assets | 6.375% | 5.75%
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in | $ 626.3 | $ 610.3
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in to Risk Weighted Assets | 7.00% | 7.00%
Well Capitalized Amount | $ 581.6 | $ 566.7
Well Capitalized Ratio | 6.50% | 6.50%
Leverage capital ratio: |  |
Actual Amount | $ 1,086.8 | $ 1,040.3
Actual Ratio | 9.28186% | 8.85532%
Adequately Capitalized Amount | $ 468.4 | $ 469.9
Adequately Capitalized Ratio | 4.00% | 4.00%
Well Capitalized Amount | $ 585.5 | $ 587.4
Well Capitalized Ratio | 5.00% | 5.00%
FIB |  |
Total risk-based capital: |  |
Actual Amount | $ 1,087.7 | $ 1,066.6
Actual Ratio | 12.20156% | 12.29128%
Capital Required for Capital Adequacy under Basel III Phase-in Schedule | $ 880.3 | $ 802.7
Capital Required for Capital Adequacy under Basel III Phase-in Schedule to Risk Weighted Assets | 9.875% | 9.25%
Capital Required for Capital Adequacy under Basel III Fully Phased-in | $ 936.0 | $ 911.2
Capital Required for Capital Adequacy under Basel III Fully Phased-in to Risk Weighted Assets | 10.50% | 10.50%
Well Capitalized Amount | $ 891.4 | $ 867.8
Well Capitalized Ratio | 10.00% | 10.00%
Tier 1 risk-based capital: |  |
Actual Amount | $ 1,013.6 | $ 994.4
Actual Ratio | 11.37045% | 11.45926%
Tier One Risk Based Capital under Basel III Phase-in Schedule | $ 702.0 | $ 629.1
Tier One Capital Required for Capital Adequacy under Basel III Phase-in Schedule to Risk Weighted Assets | 7.875% | 7.25%
Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in | $ 757.7 | $ 737.6
Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in to Risk Weighted Assets | 8.50% | 8.50%
Well Capitalized Amount | $ 713.2 | $ 694.2
Well Capitalized Ratio | 8.00% | 8.00%
Common equity tier one risk-based capital: |  |
Actual Amount | $ 1,013.6 | $ 994.4
Actual Ratio | 11.37045% | 11.45926%
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Phase-in Schedule | $ 568.3 | $ 499.0
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Phase-in Schedule to Risk Weighted Assets | 6.375% | 5.75%
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in | $ 624.0 | $ 607.4
Common Equity Tier One Capital Required for Capital Adequacy under Basel III Fully Phased-in to Risk Weighted Assets | 7.00% | 7.00%
Well Capitalized Amount | $ 579.4 | $ 564.1
Well Capitalized Ratio | 6.50% | 6.50%
Leverage capital ratio: |  |
Actual Amount | $ 1,013.6 | $ 994.4
Actual Ratio | 8.68594% | 8.48004%
Adequately Capitalized Amount | $ 466.8 | $ 469.1
Adequately Capitalized Ratio | 4.00% | 4.00%
Well Capitalized Amount | $ 583.5 | $ 586.3
Well Capitalized Ratio | 5.00% | 5.00%

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