SECURITIES - Schedule of Investments (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Securities Available-for-sale, Amortized Cost		$ 19,713	$ 17,831
Securities Available-for-sale, Gross Unrealized Gains		80	157
Securities Available-for-sale, Gross Unrealized Losses		(292)	(104)
Securities Available-for-sale, Fair Value	[1]	19,501	17,884
Securities Held-to-maturity, Amortized Cost	[1]	5,071	5,258
Securities Held-to-maturity, Gross Unrealized Gain		31	50
Securities Held-to-maturity, Gross Unrealized Losses		(44)	(11)
Securities held-to-maturity, Fair Value		5,058	5,297
Money market mutual fund, Amortized Cost		91	65
Money market mutual fund, Gross Unrealized Gains		0	0
Money market mutual fund, Gross Unrealized Losses		0	0
Money market mutual fund, Fair Value		91	65
Total other investment securities, at fair value, Amortized Cost		96	70
Total other investments securities, at fair value, Gross Unrealized Gains		0	0
Total other investments securities, at fair value, Gross Unrealized Losses		0	0
Total other investment securities, at fair value		96	70
Total other investment securities, at cost		942	863
Total other investment securities, at cost, Gross Unrealized Gain		0	0
Total other investment securities, at cost, Gross Unrealized Losses		0	0
Total other investment securities, at cost, Fair Value		942	863
U.S. Treasury and other
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities Available-for-sale, Amortized Cost		30	16
Debt Securities Available-for-sale, Gross Unrealized Gains		0	0
Debt Securities Available-for-sale, Gross Unrealized Losses		0	0
Debt Securities Available-for-sale, Fair Value		30	16
State and political subdivisions
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities Available-for-sale, Amortized Cost		8	9
Debt Securities Available-for-sale, Gross Unrealized Gains		0	0
Debt Securities Available-for-sale, Gross Unrealized Losses		0	0
Debt Securities Available-for-sale, Fair Value		8	9
Federal agencies and U.S. government sponsored entities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities Available-for-sale, Amortized Cost		19,231	17,234
Debt Securities Available-for-sale, Gross Unrealized Gains		78	153
Debt Securities Available-for-sale, Gross Unrealized Losses		(264)	(67)
Debt Securities Available-for-sale, Fair Value		19,045	17,320
Securities Held-to-maturity, Amortized Cost		4,126	4,105
Securities Held-to-maturity, Gross Unrealized Gain		12	27
Securities Held-to-maturity, Gross Unrealized Losses		(44)	(11)
Securities held-to-maturity, Fair Value		4,094	4,121
Other/non-agency
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities Available-for-sale, Amortized Cost		427	555
Debt Securities Available-for-sale, Gross Unrealized Gains		2	4
Debt Securities Available-for-sale, Gross Unrealized Losses		(28)	(37)
Debt Securities Available-for-sale, Fair Value		401	522
Securities Held-to-maturity, Amortized Cost		945	1,153
Securities Held-to-maturity, Gross Unrealized Gain		19	23
Securities Held-to-maturity, Gross Unrealized Losses		0	0
Securities held-to-maturity, Fair Value		964	1,176
Total mortgage-backed securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities Available-for-sale, Amortized Cost		19,658	17,789
Debt Securities Available-for-sale, Gross Unrealized Gains		80	157
Debt Securities Available-for-sale, Gross Unrealized Losses		(292)	(104)
Debt Securities Available-for-sale, Fair Value		19,446	17,842
Total debt securities available for sale
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities Available-for-sale, Amortized Cost		19,696	17,814
Debt Securities Available-for-sale, Gross Unrealized Gains		80	157
Debt Securities Available-for-sale, Gross Unrealized Losses		(292)	(104)
Debt Securities Available-for-sale, Fair Value		19,484	17,867
Marketable equity securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Equity Securities Available-for-sale, Amortized Cost		5	5
Equity Securities Available-for-sale, Gross Unrealized Gains		0	0
Equity Securities Available-for-sale, Gross Unrealized Losses		0	0
Equity Securities Available-for-sale, Fair Value		5	5
Other equity securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Equity Securities Available-for-sale, Amortized Cost		12	12
Equity Securities Available-for-sale, Gross Unrealized Gains		0	0
Equity Securities Available-for-sale, Gross Unrealized Losses		0	0
Equity Securities Available-for-sale, Fair Value		12	12
Total equity securities available for sale
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Equity Securities Available-for-sale, Amortized Cost		17	17
Equity Securities Available-for-sale, Gross Unrealized Gains		0	0
Equity Securities Available-for-sale, Gross Unrealized Losses		0	0
Equity Securities Available-for-sale, Fair Value		17	17
Other investments
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Other investments, Amortized Cost		5	5
Other investments, Accumulated Gross Unrealized Gains		0	0
Other investments, Accumulated Gross Unrealized Losses		0	0
Other investments, Fair Value		5	5
Federal Reserve Bank stock
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Federal Reserve Bank stock, Amortized Cost		463	468
Federal Reserve Bank stock, Gross Unrealized Gains		0	0
Federal Reserve Bank stock, Gross Unrealized Losses		0	0
Federal Reserve Bank stock, Fair Value		463	468
Federal Home Loan Bank stock
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Federal Home Loan Bank stock, Amortized Cost		479	395
Federal Home Loan Bank stock, Gross Unrealized Gain		0	0
Federal Home Loan Bank stock, Gross Unrealized Losses		0	0
Federal Home Loan Bank stock, Fair Value		$ 479	$ 395

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.