REGULATORY MATTERS - Capital and Capital Ratio Information (Details) - USD ($) $ in Millions		Mar. 31, 2016		Dec. 31, 2015
Common Equity Tier 1 to Risk-Weighted Assets (Amount)
Actual	[1]	$ 13,570	[2]	$ 13,389
Minimum Capital Adequacy	[1]	5,975	[2]	5,134
Classification as Well-capitalized	[1]	$ 7,578	[2]	$ 7,415
Common Equity Tier 1 to Risk-Weighted Assets (Ratio)
Actual	[1]	11.60%	[2]	11.70%
Minimum Capital Adequacy	[1]	5.125%	[2]	4.50%
Classification as Well-capitalized	[1]	6.50%	[2]	6.50%
Tier 1 Capital to Risk-Weighted Assets (Amount)
Actual	[3]	$ 13,817	[2]	$ 13,636
Minimum Capital Adequacy	[3]	7,724	[2]	6,845
Classification as Well-capitalized	[3]	$ 9,327	[2]	$ 9,127
Tier 1 Capital to Risk-Weighted Assets (Ratio)
Actual	[3]	11.90%	[2]	12.00%
Minimum Capital Adequacy	[3]	6.625%	[2]	6.00%
Classification as Well-capitalized	[3]	8.00%	[2]	8.00%
Total Capital to Risk-Weighted Assets (Amount)
Actual	[4]	$ 17,587	[2]	$ 17,505
Minimum Capital Adequacy	[4]	10,056	[2]	9,127
Classification as Well-capitalized	[4]	$ 11,659	[2]	$ 11,408
Total Capital to Risk-Weighted Assets (Ratio)
Actual	[4]	15.10%	[2]	15.30%
Minimum Capital Adequacy	[4]	8.625%	[2]	8.00%
Classification as Well-capitalized	[4]	10.00%	[2]	10.00%
Tier 1 Capital to Average Assets (Leverage) (Amount)
Actual	[5]	$ 13,817		$ 13,636
Minimum Capital Adequacy	[5]	5,318		5,218
Classification as Well-capitalized	[5]	$ 6,648		$ 6,523
Tier 1 Capital to Average Assets (Leverage) (Ratio)
Actual	[5]	10.40%		10.50%
Minimum Capital Adequacy	[5]	4.00%		4.00%
Classification as Well-capitalized	[5]	5.00%		5.00%
Capital Conservation Buffer		0.625%

[1] “Common equity tier 1 capital ratio” represents CET1 divided by total risk-weighted assets as defined under Basel III Standardized approach.

[2] “Minimum Capital ratio” for 2016 includes capital conservation buffer of .625%.

[3] “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.

[4] “Total capital ratio” is total capital divided by total risk-weighted assets as defined under Basel III Standardized approach.

[5] “Tier 1 leverage ratio” is tier 1 capital divided by quarterly average total assets as defined under Basel III Standardized approach.