ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Nonperforming Loans and Leases by Class (Details) - USD ($) $ in Millions		Dec. 31, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		$ 1,045	[1]	$ 1,051
Nonperforming loans including 90 days past due	[1]			1,060
Loans accruing and 90 days or more past due		26		9
GNMA loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans sold with right to repurchase		32
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	387
Nonperforming loans including 90 days past due	[1]			148
Loans accruing and 90 days or more past due		2		1
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	322
Nonperforming loans including 90 days past due	[1]			71
Loans accruing and 90 days or more past due		2		1
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	50
Nonperforming loans including 90 days past due	[1]			77
Loans accruing and 90 days or more past due		0		0
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	15
Nonperforming loans including 90 days past due	[1]			0
Loans accruing and 90 days or more past due		0		0
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	658
Nonperforming loans including 90 days past due	[1]			912
Loans accruing and 90 days or more past due		24		8
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1],[2],[3]	144
Nonperforming loans including 90 days past due	[1],[2],[3]			331
Loans accruing and 90 days or more past due	[2],[3]	18		0
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	98
Nonperforming loans including 90 days past due	[1]			135
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	[1]	243
Nonperforming loans including 90 days past due	[1]			272
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	[1]	32
Nonperforming loans including 90 days past due	[1]			38
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	[1]	33
Nonperforming loans including 90 days past due	[1]			32
Loans accruing and 90 days or more past due		0		0
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	50
Nonperforming loans including 90 days past due	[1]			42
Loans accruing and 90 days or more past due		0		0
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	38
Nonperforming loans including 90 days past due	[1]			41
Loans accruing and 90 days or more past due		5		6
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	16
Nonperforming loans including 90 days past due	[1]			16
Loans accruing and 90 days or more past due		0		0
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	4
Nonperforming loans including 90 days past due	[1]			5
Loans accruing and 90 days or more past due		$ 1		$ 2

[1] Effective March 31, 2016, the Company began excluding loans 90 days or more past due and still accruing from nonperforming loans and leases. Nonperforming loans and leases as of December 31, 2015 included loans and leases on nonaccrual of $1.051 billion and loans and leases accruing and 90 days or more past due of $9 million.

[2] Effective March 31, 2016, the Company began excluding first lien residential mortgage loans that are 100% guaranteed by the Federal Housing Administration from nonperforming balances. As of December 31, 2016, $18 million of these loans were accruing and 90 days or more past due.

[3] Effective March 31, 2016, the Company began excluding guaranteed residential mortgage loans sold to GNMA for which the Company had the right, but not the obligation, to repurchase from nonperforming balances. As of December 31, 2016 these loans totaled $32 million. These loans are consolidated on the Company’s Consolidated Balance Sheets.