ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Loans with Indicators of High Credit Risk (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
High loan-to-value
Financing Receivable, Recorded Investment [Line Items]
Total	$ 3,122	$ 3,541
High loan-to-value | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	748	773
High loan-to-value | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	1,400	1,743
High loan-to-value | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	974	1,025
High loan-to-value | Credit Cards
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Interest only/negative amortization
Financing Receivable, Recorded Investment [Line Items]
Total	961	894
Interest only/negative amortization | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	961	894
Interest only/negative amortization | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Interest only/negative amortization | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Interest only/negative amortization | Credit Cards
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Low introductory rate
Financing Receivable, Recorded Investment [Line Items]
Total	91	98
Low introductory rate | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Low introductory rate | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	1	0
Low introductory rate | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Low introductory rate | Credit Cards
Financing Receivable, Recorded Investment [Line Items]
Total	90	98
Multiple characteristics and other
Financing Receivable, Recorded Investment [Line Items]
Total	20	24
Multiple characteristics and other | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	20	24
Multiple characteristics and other | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Multiple characteristics and other | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Multiple characteristics and other | Credit Cards
Financing Receivable, Recorded Investment [Line Items]
Total	0	0
Credit risk, loans with increased credit exposure
Financing Receivable, Recorded Investment [Line Items]
Total	4,194	4,557
Credit risk, loans with increased credit exposure | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	1,729	1,691
Credit risk, loans with increased credit exposure | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	1,401	1,743
Credit risk, loans with increased credit exposure | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	974	1,025
Credit risk, loans with increased credit exposure | Credit Cards
Financing Receivable, Recorded Investment [Line Items]
Total	$ 90	$ 98