FAIR VALUE MEASUREMENTS - Schedule of Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Assets
Securities available for sale	$ 18,197	$ 18,656
Loans held for sale	369	256
Derivative assets	1,010	790
Money market mutual fund	45	28
Venture capital investments and other investments	5	5
Total other investment securities, at fair value	50	33
Total assets	19,626	19,735
Liabilities
Derivative liabilities	816	773
Total liabilities	816	773
Interest rate swaps
Assets
Derivative assets	837	613
Liabilities
Derivative liabilities	648	600
Foreign exchange contracts
Assets
Derivative assets	163	170
Liabilities
Derivative liabilities	158	164
Other contracts
Assets
Derivative assets	10	7
Liabilities
Derivative liabilities	10	9
Mortgage-backed securities
Assets
Securities available for sale	18,156	18,606
State and political subdivisions
Assets
Securities available for sale	9	10
Equity securities
Assets
Securities available for sale	17	25
U.S. Treasury
Assets
Securities available for sale	15	15
Residential loans held for sale
Assets
Loans held for sale	269	213
Commercial real estate loans held for sale
Assets
Loans held for sale	100	43
Level 1
Assets
Securities available for sale	15	23
Loans held for sale	0	0
Derivative assets	0	0
Money market mutual fund	45	28
Venture capital investments and other investments	0	0
Total other investment securities, at fair value	45	28
Total assets	60	51
Liabilities
Derivative liabilities	0	0
Total liabilities	0	0
Level 1 \| Interest rate swaps
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 1 \| Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 1 \| Other contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 1 \| Mortgage-backed securities
Assets
Securities available for sale	0	0
Level 1 \| State and political subdivisions
Assets
Securities available for sale	0	0
Level 1 \| Equity securities
Assets
Securities available for sale	0	8
Level 1 \| U.S. Treasury
Assets
Securities available for sale	15	15
Level 1 \| Residential loans held for sale
Assets
Loans held for sale	0	0
Level 1 \| Commercial real estate loans held for sale
Assets
Loans held for sale	0	0
Level 2
Assets
Securities available for sale	18,182	18,633
Loans held for sale	369	256
Derivative assets	1,010	790
Money market mutual fund	0	0
Venture capital investments and other investments	5	0
Total other investment securities, at fair value	5	0
Total assets	19,566	19,679
Liabilities
Derivative liabilities	816	773
Total liabilities	816	773
Level 2 \| Interest rate swaps
Assets
Derivative assets	837	613
Liabilities
Derivative liabilities	648	600
Level 2 \| Foreign exchange contracts
Assets
Derivative assets	163	170
Liabilities
Derivative liabilities	158	164
Level 2 \| Other contracts
Assets
Derivative assets	10	7
Liabilities
Derivative liabilities	10	9
Level 2 \| Mortgage-backed securities
Assets
Securities available for sale	18,156	18,606
Level 2 \| State and political subdivisions
Assets
Securities available for sale	9	10
Level 2 \| Equity securities
Assets
Securities available for sale	17	17
Level 2 \| U.S. Treasury
Assets
Securities available for sale	0	0
Level 2 \| Residential loans held for sale
Assets
Loans held for sale	269	213
Level 2 \| Commercial real estate loans held for sale
Assets
Loans held for sale	100	43
Level 3
Assets
Securities available for sale	0	0
Loans held for sale	0	0
Derivative assets	0	0
Money market mutual fund	0	0
Venture capital investments and other investments	0	5
Total other investment securities, at fair value	0	5
Total assets	0	5
Liabilities
Derivative liabilities	0	0
Total liabilities	0	0
Level 3 \| Interest rate swaps
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 3 \| Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 3 \| Other contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 3 \| Mortgage-backed securities
Assets
Securities available for sale	0	0
Level 3 \| State and political subdivisions
Assets
Securities available for sale	0	0
Level 3 \| Equity securities
Assets
Securities available for sale	0	0
Level 3 \| U.S. Treasury
Assets
Securities available for sale	0	0
Level 3 \| Residential loans held for sale
Assets
Loans held for sale	0	0
Level 3 \| Commercial real estate loans held for sale
Assets
Loans held for sale	$ 0	$ 0

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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The face amount of loans that will be sold to other entities.

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