ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Loans with Indicators of High Credit Risk (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
High loan-to-value
Financing Receivable, Recorded Investment [Line Items]
Total	$ 2,472	$ 3,541
High loan-to-value | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	649	773
High loan-to-value | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	1,038	1,743
High loan-to-value | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	785	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	1,110	894
Interest only/negative amortization | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	1,110	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	99	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	3	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	96	98
Multiple characteristics and other
Financing Receivable, Recorded Investment [Line Items]
Total	14	24
Multiple characteristics and other | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	14	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	3,695	4,557
Credit risk, loans with increased credit exposure | Residential Mortgages
Financing Receivable, Recorded Investment [Line Items]
Total	1,773	1,691
Credit risk, loans with increased credit exposure | Home Equity Loans and Lines of Credit
Financing Receivable, Recorded Investment [Line Items]
Total	1,041	1,743
Credit risk, loans with increased credit exposure | Home Equity Products serviced by others
Financing Receivable, Recorded Investment [Line Items]
Total	785	1,025
Credit risk, loans with increased credit exposure | Credit Cards
Financing Receivable, Recorded Investment [Line Items]
Total	$ 96	$ 98