VARIABLE INTEREST ENTITIES - Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Variable Interest Entity [Line Items]
Assets	$ 37,441	$ 34,615	$ 34,329
Liabilities	32,490	29,732
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	154	154
Liabilities	125	136
Maximum Exposure to Loss	153	153
Trust Preferred Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	1	1
Liabilities	66	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	121	120
Liabilities	51	60
Maximum Exposure to Loss	121	120
Other Investments [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	32	33
Liabilities	8	10
Maximum Exposure to Loss	$ 32	$ 33