ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Nonperforming Loans and Leases by Class (Details) - USD ($) $ in Millions		Jun. 30, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		$ 1,044	[1]	$ 1,051
Nonperforming loans including 90 days past due	[1]			1,060
Loans accruing and 90 days or more past due		26		9
Other loans held for sale		372		40
GNMA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans sold with right to repurchase		34
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	347
Nonperforming loans including 90 days past due	[1]			148
Loans accruing and 90 days or more past due		4		1
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	277
Nonperforming loans including 90 days past due	[1]			71
Loans accruing and 90 days or more past due		0		1
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	70
Nonperforming loans including 90 days past due	[1]			77
Loans accruing and 90 days or more past due		4		0
Leases
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	0
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]	697
Nonperforming loans including 90 days past due	[1]			912
Loans accruing and 90 days or more past due		22		8
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1],[2],[3],[4]	174
Nonperforming loans including 90 days past due	[1],[2],[3],[4]			331
Loans accruing and 90 days or more past due	[2],[3],[4]	15		0
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1],[4]	104
Nonperforming loans including 90 days past due	[1],[4]			135
Loans accruing and 90 days or more past due	[4]	0		0
Home equity lines of credit
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	251
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],[5]	33
Nonperforming loans including 90 days past due	[1],[5]			38
Loans accruing and 90 days or more past due	[5]	0		0
Home equity lines of credit serviced by others
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1],[5]	38
Nonperforming loans including 90 days past due	[1],[5]			32
Loans accruing and 90 days or more past due	[5]	0		0
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	43
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]	37
Nonperforming loans including 90 days past due	[1]			41
Loans accruing and 90 days or more past due		6		6
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	14
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]	3
Nonperforming loans including 90 days past due	[1]			5
Loans accruing and 90 days or more past due		1		$ 2
TDR Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other loans held for sale		322
TDR Loans | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other loans held for sale		262
TDR Loans | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other loans held for sale		60
Total Loans and Leases | TDR Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other loans held for sale		71
Total Loans and Leases | TDR Loans | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other loans held for sale		54
Total Loans and Leases | TDR Loans | Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Other loans held for sale		$ 17

[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 June 30, 2016, $15 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 June 30, 2016 these loans totaled $34 million. These loans are consolidated on the Company’s Consolidated Balance Sheets.

[4] Nonperforming balances at June 30, 2016 excluded $71 million of troubled debt restructured loans held for sale, including $54 million of residential mortgages and $17 million of home equity loans.

[5] The Company’s SBO portfolio consists of purchased home equity loans and lines that were originally serviced by others. The Company now services a portion of this portfolio internally.