Annual report pursuant to Section 13 and 15(d)

AVAILABLE-FOR-SALE AND OTHER SECURITIES - Schedule of Amortized Cost, Fair Value, and Gross Unrealized Gains/(Losses) (Details)

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AVAILABLE-FOR-SALE AND OTHER SECURITIES - Schedule of Amortized Cost, Fair Value, and Gross Unrealized Gains/(Losses) (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 15,727 $ 15,777
Gross Gains 28 48
Gross Losses (286) (262)
Fair Value 15,469 15,563
U.S. Treasury securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 5 6
Gross Gains 0 0
Gross Losses 0 0
Fair Value 5 6
Collateralized Mortgage Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6,661 6,955
Gross Gains 1 6
Gross Losses (178) (151)
Fair Value 6,484 6,810
Commercial MBS    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 2,539 3,700
Gross Gains 0 2
Gross Losses (52) (39)
Fair Value 2,487 3,663
Residential MBS    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,371 196
Gross Gains 1 5
Gross Losses (5) (1)
Fair Value 1,367 200
Other agencies    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 69 73
Gross Gains 1 0
Gross Losses 0 0
Fair Value 70 73
Total Federal agencies and other agencies    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,645 10,930
Gross Gains 3 13
Gross Losses (235) (191)
Fair Value 10,413 10,752
Municipal securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,892 3,260
Gross Gains 21 29
Gross Losses (35) (39)
Fair Value 3,878 3,250
Asset-backed securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 482 824
Gross Gains 1 2
Gross Losses (16) (32)
Fair Value 467 794
Corporate debt    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 106 195
Gross Gains 3 4
Gross Losses 0 0
Fair Value 109 199
Other securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 602 568
Gross Gains 0 0
Gross Losses 0 0
Fair Value $ 602 $ 568