Quarterly report pursuant to Section 13 or 15(d)

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

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FAIR VALUES OF ASSETS AND LIABILITIES - Fair Value Option (Details) - USD ($)
$ in Millions
Mar. 31, 2018
Dec. 31, 2017
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure $ 426 $ 413
Loans Receivable, Fair Value Disclosure 86 93
Fair Value, Measurements, Recurring    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure 426 413
Fair Value, Measurements, Recurring | Mortgages Held For Sale    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure 426 413
Loans Held For Sale Unpaid Principal 416 400
Difference (10) (13)
Fair Value, Measurements, Recurring | Mortgages Held To Maturity    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Receivable, Fair Value Disclosure 86 93
Loans Held To Maturity Unpaid Principal 94 102
Difference (8) (9)
Fair Value, Measurements, Recurring | 90 or more days | Mortgages Held For Sale    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure 1 1
Loans Held For Sale Unpaid Principal 1 1
Difference 0 0
Fair Value, Measurements, Recurring | 90 or more days | Mortgages Held To Maturity    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Receivable, Fair Value Disclosure 8 10
Loans Held To Maturity Unpaid Principal 9 11
Difference $ (1) $ (1)