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
Jun. 30, 2018
Dec. 31, 2017
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure $ 643 $ 413
Loans Receivable, Fair Value Disclosure 84 93
Fair Value, Measurements, Recurring    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure 643 413
Fair Value, Measurements, Recurring | Mortgages Held For Sale    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Held-for-sale, Fair Value Disclosure 643 413
Loans Held For Sale Unpaid Principal 625 400
Difference (18) (13)
Fair Value, Measurements, Recurring | Mortgages Held To Maturity    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Loans Receivable, Fair Value Disclosure 84 93
Loans Held To Maturity Unpaid Principal 93 102
Difference (9) (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 0 1
Loans Held For Sale Unpaid Principal 0 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 7 10
Loans Held To Maturity Unpaid Principal 8 11
Difference $ (1) $ (1)