REGULATORY MATTERS - Capital and Capital Ratio Information (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Common Equity Tier 1 to Risk-Weighted Assets (Amount)
Actual	$ 14,304	$ 14,485
Minimum Capital Adequacy	$ 10,004	$ 8,683
Common Equity Tier 1 to Risk-Weighted Assets (Ratio)
Actual	10.00%	10.60%
Minimum Capital Adequacy	7.00%	6.375%
Tier 1 Capital to Risk-Weighted Assets (Amount)
Actual	$ 15,874	$ 15,325
Minimum Capital Adequacy	$ 12,148	$ 10,726
Tier 1 Capital to Risk-Weighted Assets (Ratio)
Actual	11.10%	11.30%
Minimum Capital Adequacy	8.50%	7.875%
Total Capital to Risk-Weighted Assets (Amount)
Actual	$ 18,542	$ 18,157
Minimum Capital Adequacy	$ 15,006	$ 13,450
Total Capital to Risk-Weighted Assets (Ratio)
Actual	13.00%	13.30%
Minimum Capital Adequacy	10.50%	9.875%
Tier 1 Capital to Average Assets (Leverage) (Amount)
Actual	$ 15,874	$ 15,325
Minimum Capital Adequacy	$ 6,351	$ 6,121
Tier 1 Capital to Average Assets (Leverage) (Ratio)
Actual	10.00%	10.00%
Minimum Capital Adequacy	4.00%	4.00%
Capital conservation buffer	2.50%	1.875%

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Capital Ratios [Abstract]

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The minimum common equity tier 1 ratio (CET1 divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Amount of Common Equity Tier One Risk-based Capital, as defined by regulatory framework.

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Percentage of Common Equity Tier One Risk-based Capital to total risk-weighted assets, as defined by regulatory framework.

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Amount of Common Equity Tier 1 Risk-based Capital required to be categorized as adequately capitalized under regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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