Annual report pursuant to Section 13 and 15(d)

INVESTMENT SECURITIES AND OTHER SECURITIES - Realized Securities Gains (Losses) (Details)

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INVESTMENT SECURITIES AND OTHER SECURITIES - Realized Securities Gains (Losses) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]      
Pledged Financial Instruments, Not Separately Reported, Securities for Other Debt Facilities $ 3,800 $ 4,500  
Available-for-sale Securities, Gross Realized Gains 11 7 $ 10
Available-for-sale Securities, Gross Realized Losses (35) (28) (10)
Debt and Equity Securities, Gain (Loss) (24) (21) 0
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities 0 0 (4)
Available-for-sale Securities, Gross Realized Gain (Loss) (24) (21) (4)
Payments to Acquire Available-for-sale Securities $ 6,036 $ 2,485 $ 5,429