ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Nonperforming Loans and Leases by Class (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		$ 1,050	$ 1,045
Loans accruing and 90 days or more past due		26	26
GNMA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans sold with right to repurchase		31	32
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		413	387
Loans accruing and 90 days or more past due		5	2
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		367	322
Loans accruing and 90 days or more past due		5	2
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		46	50
Loans accruing and 90 days or more past due		0	0
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		0	15
Loans accruing and 90 days or more past due		0	0
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		637	658
Loans accruing and 90 days or more past due		21	24
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1],[2]	142	144
Loans accruing and 90 days or more past due	[1],[2]	13	18
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		89	98
Loans accruing and 90 days or more past due		0	0
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		238	243
Loans accruing and 90 days or more past due		0	0
Home equity loans serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		29	32
Loans accruing and 90 days or more past due		0	0
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		30	33
Loans accruing and 90 days or more past due		0	0
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		52	50
Loans accruing and 90 days or more past due		0	0
Education
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		38	38
Loans accruing and 90 days or more past due		4	5
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		16	16
Loans accruing and 90 days or more past due		0	0
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		3	4
Loans accruing and 90 days or more past due		$ 4	$ 1

[1] Nonperforming balances exclude first lien residential mortgage loans that are 100% guaranteed by the Federal Housing Administration. These loans, which are accruing and 90 days or more past due, totaled $13 million and $18 million as of March 31, 2017 and December 31, 2016, respectively.

[2] Nonperforming balances exclude guaranteed residential mortgage loans sold to GNMA for which the Company has the right, but not the obligation, to repurchase. These loans totaled $31 million and $32 million as of March 31, 2017 and December 31, 2016, respectively. These loans are consolidated on the Company’s Consolidated Balance Sheets.