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GOODWILL - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
GOODWILL - Narrative (Details) $ in Millions	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) reporting_unit	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Goodwill [Line Items]
Number of reporting units \| reporting_unit			2
Goodwill acquired			$ 6
Goodwill impairment loss	$ 0	$ 0	0	$ 0
Amortization of intangibles			6	$ 8
Consumer Banking
Goodwill [Line Items]
Goodwill acquired			0
Goodwill accumulated impairment loss	5,900		5,900		$ 5,900
Commercial Banking
Goodwill [Line Items]
Goodwill acquired			6
Goodwill accumulated impairment loss	$ 50		$ 50		$ 50