VARIABLE INTEREST ENTITIES - Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Variable Interest Entity [Line Items]
Assets	$ 39,361	$ 37,354	$ 37,441
Liabilities	34,263	32,395
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	140	146
Liabilities	108	119
Maximum Exposure to Loss	139	145
Trust Preferred Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	1	1
Liabilities	67	66
Maximum Exposure to Loss	0	0
Affordable Housing Tax Credit Partnerships [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	113	119
Liabilities	37	45
Maximum Exposure to Loss	113	119
Other Investments [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	26	26
Liabilities	4	8
Maximum Exposure to Loss	$ 26	$ 26