ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Nonperforming Loans and Leases by Class (Details) - USD ($)		Sep. 30, 2016		Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans		$ 1,107,000,000	[1]	$ 1,051,000,000
Nonperforming loans including 90 days past due	[1]			1,060,000,000
Loans accruing and 90 days or more past due		24,000,000		9,000,000
Other loans held for sale		0		40,000,000
GNMA
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans sold with right to repurchase		32,000,000
Commercial Banking
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	396,000,000
Nonperforming loans including 90 days past due	[1]			148,000,000
Loans accruing and 90 days or more past due		1,000,000		1,000,000
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	334,000,000
Nonperforming loans including 90 days past due	[1]			71,000,000
Loans accruing and 90 days or more past due		1,000,000		1,000,000
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	62,000,000
Nonperforming loans including 90 days past due	[1]			77,000,000
Loans accruing and 90 days or more past due		0		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]	711,000,000
Nonperforming loans including 90 days past due	[1]			912,000,000
Loans accruing and 90 days or more past due		23,000,000		8,000,000
Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1],[2],[3]	170,000,000
Nonperforming loans including 90 days past due	[1],[2],[3]			331,000,000
Loans accruing and 90 days or more past due	[2],[3]	16,000,000		0
Home equity loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	105,000,000
Nonperforming loans including 90 days past due	[1]			135,000,000
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]	249,000,000
Nonperforming loans including 90 days past due	[1]			272,000,000
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]	32,000,000
Nonperforming loans including 90 days past due	[1]			38,000,000
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]	42,000,000
Nonperforming loans including 90 days past due	[1]			32,000,000
Loans accruing and 90 days or more past due		0		0
Automobile
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	55,000,000
Nonperforming loans including 90 days past due	[1]			42,000,000
Loans accruing and 90 days or more past due		0		0
Student
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	38,000,000
Nonperforming loans including 90 days past due	[1]			41,000,000
Loans accruing and 90 days or more past due		6,000,000		6,000,000
Credit cards
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	16,000,000
Nonperforming loans including 90 days past due	[1]			16,000,000
Loans accruing and 90 days or more past due		0		0
Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonperforming loans	[1]	4,000,000
Nonperforming loans including 90 days past due	[1]			5,000,000
Loans accruing and 90 days or more past due		$ 1,000,000		$ 2,000,000

[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 September 30, 2016, $16 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 September 30, 2016 these loans totaled $32 million. These loans are consolidated on the Company’s Consolidated Balance Sheets.