Annual report pursuant to Section 13 and 15(d)

FAIR VALUES OF ASSETS AND LIABILITIES - Fair Value Option-Changes in Fair Value (Details)

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FAIR VALUES OF ASSETS AND LIABILITIES - Fair Value Option-Changes in Fair Value (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Fair Value, Measurements, Recurring [Member]      
Fair Value, Option, Quantitative Disclosures [Line Items]      
Net gains (losses) from fair value changes $ 8 $ 7 $ (2)
Loans held for investment      
Fair Value, Option, Quantitative Disclosures [Line Items]      
Net gains (losses) from fair value changes $ 0 $ 0 $ (1)