REGULATORY MATTERS - Capital and Capital Ratio Information (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Common Equity Tier 1 to Risk-Weighted Assets (Amount)
Actual	[1]	$ 13,389
Minimum Capital Adequacy	[1]	5,134
Classification as Well-capitalized	[1]	$ 7,415
Common Equity Tier 1 to Risk-Weighted Assets (Ratio)
Actual	[1]	11.70%
Minimum Capital Adequacy	[1]	4.50%
Classification as Well-capitalized	[1]	6.50%
Tier 1 Common Equity to Risk-Weighted Assets
Tier 1 Common Equity	[1]		$ 13,173
Tier One Common Equity To Risk Weighted Assets	[1]		12.40%
Tier 1 Capital to Risk-Weighted Assets (Amount)
Actual	[2]	$ 13,636	$ 13,173
Minimum Capital Adequacy	[2]	6,845	4,239
Classification as Well-capitalized	[2]	$ 9,127	$ 6,358
Tier 1 Capital to Risk-Weighted Assets (Ratio)
Actual	[2]	12.00%	12.40%
Minimum Capital Adequacy	[2]	6.00%	4.00%
Classification as Well-capitalized	[2]	8.00%	6.00%
Total Capital to Risk-Weighted Assets (Amount)
Actual	[3]	$ 17,505	$ 16,781
Minimum Capital Adequacy	[3]	9,127	8,477
Classification as Well-capitalized	[3]	$ 11,408	$ 10,596
Total Capital to Risk-Weighted Assets (Ratio)
Actual	[3]	15.30%	15.80%
Minimum Capital Adequacy	[3]	8.00%	8.00%
Classification as Well-capitalized	[3]	10.00%	10.00%
Tier 1 Capital to Average Assets (Leverage) (Amount)
Actual	[4]	$ 13,636	$ 13,173
Minimum Capital Adequacy	[4]	5,218	4,982
Classification as Well-capitalized	[4]	$ 6,523	$ 6,227
Tier 1 Capital to Average Assets (Leverage) (Ratio)
Actual	[4]	10.50%	10.60%
Minimum Capital Adequacy	[4]	4.00%	4.00%
Classification as Well-capitalized	[4]	5.00%	5.00%

[1] CET1 under Basel III replaced the concept of tier 1 common capital that existed under Basel I effective January 1, 2015. “Common equity tier 1 capital ratio” as of December 31, 2015 represents CET1 divided by total risk-weighted assets as defined under Basel III Standardized approach. The “tier 1 common capital ratio” reported prior to January 1, 2015, represented tier 1 common equity divided by total risk-weighted assets as defined under the Basel I general risk-based capital rule.

[2] “Tier 1 capital ratio” is tier 1 capital, which includes CET1 capital plus non-cumulative perpetual preferred equity that qualifies as additional tier 1 capital, divided by total risk-weighted assets as defined under Basel III Standardized approach. The “tier 1 capital ratio” reported prior to January 1, 2015, represented tier 1 capital divided by total risk-weighted assets as defined under the Basel I general risk-based capital rule.

[3] “Total capital ratio” is total capital divided by total risk-weighted assets as defined under Basel III Standardized approach. The “Total capital ratio” reported prior to January 1, 2015, represented total capital divided by total risk-weighted assets as defined under the Basel I general risk-based capital rule.

[4] “Tier 1 leverage ratio” is tier 1 capital divided by quarterly average total assets as defined under Basel III Standardized approach. The “tier 1 leverage ratio” reported prior to January 1, 2015, represented tier 1 capital divided by quarterly average total assets as defined under the Basel I general risk-based capital rule.