NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,119	[1]
Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	786
Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	333
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	513	[1]
Service charges and fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	408
Service charges and fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	105
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	244	[1]
Card fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	207
Card fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	37
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	181	[1]
Capital markets fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Capital markets fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	181
Trust and investment services fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	171	[1]
Trust and investment services fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	171
Trust and investment services fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	[1]
Other banking fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0
Other banking fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 10

[1] There is no revenue from contracts with customers included in Other non-segment operations.