VARIABLE INTEREST ENTITIES - Income Statement Effect (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Non-Interest Income
Amortization of tax credit investments under equity method, net of tax benefit	$ 1	$ 1	$ 1	$ 1
Provision for income taxes:
Amortization of LIHTC investments under proportional method	3	2	6	4
Low-income housing tax credits	(3)	(2)	(6)	(4)
Other tax benefits related to tax credit investments	(1)	(1)	(2)	(1)
Amortization Method Qualified Affordable Housing Project Investments, Provision For Income Tax	$ (1)	$ (1)	$ (2)	$ (1)