FAIR VALUE MEASUREMENTS - Schedule of Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Assets
Securities available for sale	$ 18,662	$ 18,656
Loans held for sale	397	256
Derivative assets	822	790
Venture capital investments and other investments	5	5
Total assets	19,886	19,707
Liabilities
Derivative liabilities	713	773
Total liabilities	713	773
Interest rate swaps
Assets
Derivative assets	639	613
Liabilities
Derivative liabilities	540	600
Foreign exchange contracts
Assets
Derivative assets	172	170
Liabilities
Derivative liabilities	167	164
Other contracts
Assets
Derivative assets	11	7
Liabilities
Derivative liabilities	6	9
Mortgage-backed securities
Assets
Securities available for sale	18,606	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	30	15
Residential loans held for sale
Assets
Loans held for sale	318	213
Commercial real estate loans held for sale
Assets
Loans held for sale	79	43
Level 1
Assets
Securities available for sale	30	23
Loans held for sale	0	0
Derivative assets	0	0
Venture capital investments and other investments	0	0
Total assets	30	23
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	30	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	18,632	18,633
Loans held for sale	397	256
Derivative assets	822	790
Venture capital investments and other investments	4	0
Total assets	19,855	19,679
Liabilities
Derivative liabilities	713	773
Total liabilities	713	773
Level 2 \| Interest rate swaps
Assets
Derivative assets	639	613
Liabilities
Derivative liabilities	540	600
Level 2 \| Foreign exchange contracts
Assets
Derivative assets	172	170
Liabilities
Derivative liabilities	167	164
Level 2 \| Other contracts
Assets
Derivative assets	11	7
Liabilities
Derivative liabilities	6	9
Level 2 \| Mortgage-backed securities
Assets
Securities available for sale	18,606	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	318	213
Level 2 \| Commercial real estate loans held for sale
Assets
Loans held for sale	79	43
Level 3
Assets
Securities available for sale	0	0
Loans held for sale	0	0
Derivative assets	0	0
Venture capital investments and other investments	1	5
Total assets	1	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

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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