FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held to maturity, carrying value	[1]	$ 5,071	$ 5,258
Securities held-to-maturity, fair value		5,058	5,297
Other investment securities, at cost, carrying value		942	863
Other investment securities, at cost, fair value		942	863
Other loans held for sale, carrying value		42	40
Other loans held for sale, fair value		42	40
Loans and leases, carrying value		107,669	99,042
Loans and leases, fair value		107,537	99,026
Deposits, carrying value		109,804	102,539
Deposits, fair value		109,796	102,528
Federal funds purchased and securities sold under agreements to repurchase, carrying value		1,148	802
Federal funds purchased and securities sold under agreements to repurchase, fair value		1,148	802
Other short-term borrowed funds, carrying value		3,211	2,630
Other short-term borrowed funds, fair value		3,211	2,630
Long-term borrowed funds, carrying value		12,790	9,886
Long-term borrowed funds, fair value		12,849	9,837
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held to maturity, carrying value		0	0
Securities held-to-maturity, fair value		0	0
Other investment securities, at cost, carrying value		0	0
Other investment securities, at cost, fair value		0	0
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Loans and leases, carrying value		0	0
Loans and leases, fair value		0	0
Deposits, carrying value		0	0
Deposits, fair value		0	0
Federal funds purchased and securities sold under agreements to repurchase, carrying value		0	0
Federal funds purchased and securities sold under agreements to repurchase, fair value		0	0
Other short-term borrowed funds, carrying value		0	0
Other short-term borrowed funds, fair value		0	0
Long-term borrowed funds, carrying value		0	0
Long-term borrowed funds, fair value		0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held to maturity, carrying value		5,071	5,258
Securities held-to-maturity, fair value		5,058	5,297
Other investment securities, at cost, carrying value		942	863
Other investment securities, at cost, fair value		942	863
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Loans and leases, carrying value		355	60
Loans and leases, fair value		355	60
Deposits, carrying value		109,804	102,539
Deposits, fair value		109,796	102,528
Federal funds purchased and securities sold under agreements to repurchase, carrying value		1,148	802
Federal funds purchased and securities sold under agreements to repurchase, fair value		1,148	802
Other short-term borrowed funds, carrying value		3,211	2,630
Other short-term borrowed funds, fair value		3,211	2,630
Long-term borrowed funds, carrying value		12,790	9,886
Long-term borrowed funds, fair value		12,849	9,837
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities held to maturity, carrying value		0	0
Securities held-to-maturity, fair value		0	0
Other investment securities, at cost, carrying value		0	0
Other investment securities, at cost, fair value		0	0
Other loans held for sale, carrying value		42	40
Other loans held for sale, fair value		42	40
Loans and leases, carrying value		107,314	98,982
Loans and leases, fair value		107,182	98,966
Deposits, carrying value		0	0
Deposits, fair value		0	0
Federal funds purchased and securities sold under agreements to repurchase, carrying value		0	0
Federal funds purchased and securities sold under agreements to repurchase, fair value		0	0
Other short-term borrowed funds, carrying value		0	0
Other short-term borrowed funds, fair value		0	0
Long-term borrowed funds, carrying value		0	0
Long-term borrowed funds, fair value		$ 0	$ 0

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