FAIR VALUE MEASUREMENT - Items Measured at Fair Value on a Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Level 2
Items Measured at Fair Value on a Nonrecurring Basis
Loans held-for-sale	$ 1,906	$ 1,084
Other real estate owned	22	21
Loans	677	2,881
Total assets	2,605	3,986
Level 3
Items Measured at Fair Value on a Nonrecurring Basis
Loans held-for-sale	4,169	3,068
Other real estate owned	95	81
Loans	376	486
Total assets	4,640	3,635
Fair value
Items Measured at Fair Value on a Nonrecurring Basis
Loans held-for-sale	6,075	4,152
Other real estate owned	117	102
Loans	1,053	3,367
Total assets	$ 7,245	$ 7,621