REGULATORY MATTERS - Capital and Capital Ratio Information (Details) $ in Millions	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Common Equity Tier 1 to Risk-Weighted Assets (Amount)
Actual	$ 15,656	$ 14,607
Minimum Capital Adequacy	$ 12,548	$ 11,596
Common Equity Tier 1 to Risk-Weighted Assets (Ratio)
Actual	0.099	0.100
Minimum Capital Adequacy	7.90%	7.90%
Tier 1 Capital to Risk-Weighted Assets (Amount)
Actual	$ 17,670	$ 16,572
Minimum Capital Adequacy	$ 14,930	$ 13,797
Tier 1 Capital to Risk-Weighted Assets (Ratio)
Actual	0.111	0.113
Minimum Capital Adequacy	0.094	0.094
Total Capital to Risk-Weighted Assets (Amount)
Actual	$ 20,244	$ 19,602
Minimum Capital Adequacy	$ 18,107	$ 16,733
Total Capital to Risk-Weighted Assets (Ratio)
Actual	0.127	0.134
Minimum Capital Adequacy	0.114	0.114
Tier 1 Capital to Average Assets (Leverage) (Amount)
Actual	$ 17,670	$ 16,572
Minimum Capital Adequacy	$ 7,272	$ 7,015
Tier 1 Capital to Average Assets (Leverage) (Ratio)
Actual	0.097	0.094
Minimum Capital Adequacy	0.040	0.040
Capital conservation buffer	3.40%	3.40%