FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	$ 93,410	[1],[2]	$ 85,859	[1],[2]
Loans and leases	93,674		85,724
Other loans held for sale	25		1,078
Other loans held for sale	25		1,078
Securities held to maturity	5,148		4,315
Securities held-to-maturity	5,193		4,257
Other investment securities	872		935
Other investment securities	872		935
Deposits	95,707		86,903
Deposits	95,710		86,907
Deposits held for sale	0		5,277
Deposits held for sale			5,277
Federal funds purchased and securities sold under agreements to repurchase	4,276		4,791
Federal funds purchased and securities sold under agreements to repurchase	4,276		4,791
Other short-term borrowed funds	6,253		2,251
Other short-term borrowed funds	6,253		2,249
Long-term borrowed funds	4,642		1,405
Long-term borrowed funds	4,706		1,404
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	93,410		85,859
Other loans held for sale	25		1,078
Securities held to maturity	5,148		4,315
Other investment securities	872		935
Deposits	95,707		86,903
Deposits held for sale			5,277
Federal funds purchased and securities sold under agreements to repurchase	4,276		4,791
Other short-term borrowed funds	6,253		2,251
Long-term borrowed funds	4,642		1,405
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	0		0
Other loans held for sale	0		0
Securities held-to-maturity	0		0
Other investment securities	0		0
Deposits	0		0
Deposits held for sale			0
Federal funds purchased and securities sold under agreements to repurchase	0		0
Other short-term borrowed funds	0		0
Long-term borrowed funds	0		0
Level 1 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	0		0
Other loans held for sale	0		0
Securities held to maturity	0		0
Other investment securities	0		0
Deposits	0		0
Deposits held for sale			0
Federal funds purchased and securities sold under agreements to repurchase	0		0
Other short-term borrowed funds	0		0
Long-term borrowed funds	0		0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	102		74
Other loans held for sale	0		0
Securities held-to-maturity	5,193		4,257
Other investment securities	872		935
Deposits	95,710		86,907
Deposits held for sale			5,277
Federal funds purchased and securities sold under agreements to repurchase	4,276		4,791
Other short-term borrowed funds	6,253		2,249
Long-term borrowed funds	4,706		1,404
Level 2 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	102		74
Other loans held for sale	0		0
Securities held to maturity	5,148		4,315
Other investment securities	872		935
Deposits	95,707		86,903
Deposits held for sale			5,277
Federal funds purchased and securities sold under agreements to repurchase	4,276		4,791
Other short-term borrowed funds	6,253		2,251
Long-term borrowed funds	4,642		1,405
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	93,572		85,650
Other loans held for sale	25		1,078
Securities held-to-maturity	0		0
Other investment securities	0		0
Deposits	0		0
Deposits held for sale			0
Federal funds purchased and securities sold under agreements to repurchase	0		0
Other short-term borrowed funds	0		0
Long-term borrowed funds	0		0
Level 3 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans and leases	93,308		85,785
Other loans held for sale	25		1,078
Securities held to maturity	0		0
Other investment securities	0		0
Deposits	0		0
Deposits held for sale			0
Federal funds purchased and securities sold under agreements to repurchase	0		0
Other short-term borrowed funds	0		0
Long-term borrowed funds	$ 0		$ 0

[1] Excluded from the table above are loans held for sale totaling $281 million as of December 31, 2014 and $1.3 billion as of December 31, 2013. The December 31, 2013 loans held for sale balance primarily related to the Chicago Divestiture. For further discussion, see Note 17 “Divestitures and Branch Assets and Liabilities Held for Sale.”

[2] Mortgage loans serviced for others by the Company's subsidiaries are not included above, and amounted to $17.9 billion and $18.7 billion at December 31, 2014 and 2013, respectively.