REGULATORY MATTERS - Capital and Capital Ratio Information (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Common Equity Tier 1 to Risk-Weighted Assets (Amount)
Actual	$ 13,200
Minimum Capital Adequacy	5,052
Classification as Well-capitalized	$ 7,298
Common Equity Tier 1 to Risk-Weighted Assets (Ratio)
Actual	11.80%
Minimum Capital Adequacy	4.50%
Classification as Well-capitalized	6.50%
Tier 1 Common Equity to Risk-Weighted Assets
Tier 1 Common Equity		$ 13,173
Tier One Common Equity To Risk Weighted Assets		12.40%
Tier 1 Capital to Risk-Weighted Assets (Amount)
Actual	$ 13,447	$ 13,173
Minimum Capital Adequacy	6,737	4,239
Classification as Well-capitalized	$ 8,982	$ 6,358
Tier 1 Capital to Risk-Weighted Assets (Ratio)
Actual	12.00%	12.40%
Minimum Capital Adequacy	6.00%	4.00%
Classification as Well-capitalized	8.00%	6.00%
Total Capital to Risk-Weighted Assets (Amount)
Actual	$ 17,307	$ 16,781
Minimum Capital Adequacy	8,982	8,477
Classification as Well-capitalized	$ 11,228	$ 10,596
Total Capital to Risk-Weighted Assets (Ratio)
Actual	15.40%	15.80%
Minimum Capital Adequacy	8.00%	8.00%
Classification as Well-capitalized	10.00%	10.00%
Tier 1 Capital to Average Assets (Leverage) (Amount)
Actual	$ 13,447	$ 13,173
Minimum Capital Adequacy	5,173	4,982
Classification as Well-capitalized	$ 6,467	$ 6,227
Tier 1 Capital to Average Assets (Leverage) (Ratio)
Actual	10.40%	10.60%
Minimum Capital Adequacy	4.00%	4.00%
Classification as Well-capitalized	5.00%	5.00%