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Regulatory and Capital Adequacy - Capital Ratios Under Basel III (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
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Common equity Tier 1 capital: |  |
Common equity Tier 1 capital | $ 38,162 | $ 33,071
Common equity Tier 1 capital, capital ratio | 12.20% | 11.20%
Common equity Tier 1 capital, minimum capital adequacy | 4.50% | 4.50%
Tier 1 risk-based capital: |  |
Tier 1 capital | $ 43,015 | $ 37,431
Tier 1 capital, capital ratio | 13.70% | 12.70%
Tier 1 capital, minimum capital adequacy | 6.00% | 6.00%
Tier 1 capital, well-capitalized | 6.00% | 6.00%
Total risk-based capital: |  |
Total capital | $ 50,348 | $ 44,645
Total capital, capital ratio | 16.10% | 15.10%
Total capital, minimum capital adequacy | 8.00% | 8.00%
Total capital, well-capitalized | 10.00% | 10.00%
Tier 1 leverage capital: |  |
Tier 1 leverage capital | $ 43,015 | $ 37,431
Tier 1 leverage, capital ratio | 11.70% | 10.70%
Tier 1 leverage, minimum capital adequacy | 4.00% | 4.00%
Supplementary leverage: |  |
Tier one capital under BaselIII standardized approach | $ 43,015 | $ 37,431
Basel III Supplementary Leverage Ratio | 9.90% | 9.00%
Minimum Capital Adequacy for Supplementary Leverage Ratio | 3.00% | 3.00%
Capital One Bank (USA), N.A. |  |
Common equity Tier 1 capital: |  |
Common equity Tier 1 capital | $ 17,883 | $ 16,378
Common equity Tier 1 capital, capital ratio | 16.10% | 15.30%
Common equity Tier 1 capital, minimum capital adequacy | 4.50% | 4.50%
Common equity Tie 1 capital, well capitalized | 6.50% | 6.50%
Tier 1 risk-based capital: |  |
Tier 1 capital | $ 17,883 | $ 16,378
Tier 1 capital, capital ratio | 16.10% | 15.30%
Tier 1 capital, minimum capital adequacy | 6.00% | 6.00%
Tier 1 capital, well-capitalized | 8.00% | 8.00%
Total risk-based capital: |  |
Total capital | $ 20,109 | $ 18,788
Total capital, capital ratio | 18.10% | 17.60%
Total capital, minimum capital adequacy | 8.00% | 8.00%
Total capital, well-capitalized | 10.00% | 10.00%
Tier 1 leverage capital: |  |
Tier 1 leverage capital | $ 17,883 | $ 16,378
Tier 1 leverage, capital ratio | 14.80% | 14.00%
Tier 1 leverage, minimum capital adequacy | 4.00% | 4.00%
Tier 1 leverage, well-capitalized | 5.00% | 5.00%
Supplementary leverage: |  |
Tier one capital under BaselIII standardized approach | $ 17,883 | $ 16,378
Basel III Supplementary Leverage Ratio | 12.10% | 11.50%
Minimum Capital Adequacy for Supplementary Leverage Ratio | 3.00% | 3.00%
Capital One, N.A. |  |
Common equity Tier 1 capital: |  |
Common equity Tier 1 capital | $ 28,445 | $ 25,637
Common equity Tier 1 capital, capital ratio | 13.40% | 13.00%
Common equity Tier 1 capital, minimum capital adequacy | 4.50% | 4.50%
Common equity Tie 1 capital, well capitalized | 6.50% | 6.50%
Tier 1 risk-based capital: |  |
Tier 1 capital | $ 28,445 | $ 25,637
Tier 1 capital, capital ratio | 13.40% | 13.00%
Tier 1 capital, minimum capital adequacy | 6.00% | 6.00%
Tier 1 capital, well-capitalized | 8.00% | 8.00%
Total risk-based capital: |  |
Total capital | $ 30,852 | $ 27,912
Total capital, capital ratio | 14.50% | 14.20%
Total capital, minimum capital adequacy | 8.00% | 8.00%
Total capital, well-capitalized | 10.00% | 10.00%
Tier 1 leverage capital: |  |
Tier 1 leverage capital | $ 28,445 | $ 25,637
Tier 1 leverage, capital ratio | 9.20% | 9.10%
Tier 1 leverage, minimum capital adequacy | 4.00% | 4.00%
Tier 1 leverage, well-capitalized | 5.00% | 5.00%
Supplementary leverage: |  |
Tier one capital under BaselIII standardized approach | $ 28,445 | $ 25,637
Basel III Supplementary Leverage Ratio | 8.20% | 8.00%
Minimum Capital Adequacy for Supplementary Leverage Ratio | 3.00% | 3.00%

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