Quarterly report pursuant to Section 13 or 15(d)

HELD-TO-MATURITY SECURITIES - Contractual Maturities (Details)

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HELD-TO-MATURITY SECURITIES - Contractual Maturities (Details) - USD ($)
$ in Millions
Sep. 30, 2018
Dec. 31, 2017
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Amortized Cost $ 8,465 $ 9,091
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value 8,112 8,971
Collateralized Mortgage Obligations [Member]    
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Held-to-maturity Securities, 6-10 years 36 0
Held-to-maturity Securities, Over 10 years 2,167 3,714
Amortized Cost 2,203 3,714
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value, 6-10 years 35 0
Fair Value, Over 10 years 2,073 3,657
Fair Value 2,108 3,657
Residential Mortgage Backed Securities [Member]    
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Held-to-maturity Securities, 6-10 years 0 28
Held-to-maturity Securities, Over 10 years 1,624 1,021
Amortized Cost 1,624 1,049
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value, 6-10 years 0 28
Fair Value, Over 10 years 1,555 1,016
Fair Value 1,555 1,044
Commercial Mortgage Backed Securities [Member]    
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Held-to-maturity Securities, 1-5 years 0 38
Held-to-maturity Securities, 6-10 years 130 1
Held-to-maturity Securities, Over 10 years 4,141 3,752
Amortized Cost 4,271 3,791
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value, 1-5 years 0 37
Fair Value, 6-10 years 126 1
Fair Value, Over 10 years 3,968 3,698
Fair Value 4,094 3,736
Federal agencies, Other agencies    
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Held-to-maturity Securities, 1-5 years 12 7
Held-to-maturity Securities, 6-10 years 204 362
Held-to-maturity Securities, Over 10 years 146 163
Amortized Cost 362 532
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value, 1-5 years 12 8
Fair Value, 6-10 years 197 360
Fair Value, Over 10 years 141 161
Fair Value 350 529
Total U.S. Treasury, Federal agency and other agency securities    
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Amortized Cost 8,460 9,086
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value 8,107 8,966
Municipal securities    
Debt Securities, Held-to-maturity, Maturity, Amortized Cost, Net [Abstract]    
Held-to-maturity Securities, Over 10 years 5 5
Amortized Cost 5 5
Debt Securities, Held-to-maturity, Maturity, Fair Value [Abstract]    
Fair Value, Over 10 years 5 5
Fair Value $ 5 $ 5