Annual report pursuant to Section 13 and 15(d)

HELD-TO-MATURITY SECURITIES - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, & Fair Value (Details)

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HELD-TO-MATURITY SECURITIES - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, & Fair Value (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Held-to-maturity Securities [Abstract]    
Amortized Cost $ 9,091 $ 7,807
Unrealized Gross Gains 4 22
Unrealized Gross Losses (124) (42)
Fair Value 8,971 7,787
Collateralized Mortgage Obligations [Member]    
Held-to-maturity Securities [Abstract]    
Amortized Cost 3,714 4,189
Unrealized Gross Gains 1 7
Unrealized Gross Losses (58) (33)
Fair Value 3,657 4,163
Residential MBS    
Held-to-maturity Securities [Abstract]    
Amortized Cost 1,049 98
Unrealized Gross Gains 2 3
Unrealized Gross Losses (7) 0
Fair Value 1,044 101
Commercial MBS    
Held-to-maturity Securities [Abstract]    
Amortized Cost 3,791 2,911
Unrealized Gross Gains 0 10
Unrealized Gross Losses (55) (5)
Fair Value 3,736 2,916
Other agencies    
Held-to-maturity Securities [Abstract]    
Amortized Cost 532 603
Unrealized Gross Gains 1 2
Unrealized Gross Losses (4) (4)
Fair Value 529 601
Total Federal agencies and other agencies    
Held-to-maturity Securities [Abstract]    
Amortized Cost 9,086 7,801
Unrealized Gross Gains 4 22
Unrealized Gross Losses (124) (42)
Fair Value 8,966 7,781
Municipal securities    
Held-to-maturity Securities [Abstract]    
Amortized Cost 5 6
Unrealized Gross Gains 0 0
Unrealized Gross Losses 0 0
Fair Value $ 5 $ 6