Quarterly report pursuant to Section 13 or 15(d)

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

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AVAILABLE-FOR-SALE SECURITIES - Schedule of Amortized Cost, Fair Value, and Gross Unrealized Gains and Losses (Details) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 14,539 $ 15,127
Unrealized Gross Gains 13 28
Unrealized Gross Losses (482) (286)
Fair Value 14,070 14,869
U.S. Treasury    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 6 5
Unrealized Gross Gains 0 0
Unrealized Gross Losses 0 0
Fair Value 6 5
Collateralized Mortgage Obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 7,554 6,661
Unrealized Gross Gains 0 1
Unrealized Gross Losses (304) (178)
Fair Value 7,250 6,484
Residential Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 678 1,371
Unrealized Gross Gains 0 1
Unrealized Gross Losses (19) (5)
Fair Value 659 1,367
Commercial Mortgage Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 1,815 2,539
Unrealized Gross Gains 0 0
Unrealized Gross Losses (72) (52)
Fair Value 1,743 2,487
Federal agencies, Other agencies    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 188 69
Unrealized Gross Gains 0 1
Unrealized Gross Losses (5) 0
Fair Value 183 70
Total U.S. Treasury, Federal agency and other agency securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,241 10,645
Unrealized Gross Gains 0 3
Unrealized Gross Losses (400) (235)
Fair Value 9,841 10,413
Municipal securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 3,826 3,892
Unrealized Gross Gains 12 21
Unrealized Gross Losses (73) (35)
Fair Value 3,765 3,878
Asset-backed securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 381 482
Unrealized Gross Gains 0 1
Unrealized Gross Losses (8) (16)
Fair Value 373 467
Corporate debt    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 87 106
Unrealized Gross Gains 1 3
Unrealized Gross Losses (1) 0
Fair Value 87 109
Other securities/Sovereign debt    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 4 2
Unrealized Gross Gains 0 0
Unrealized Gross Losses 0 0
Fair Value $ 4 $ 2