VARIABLE INTEREST ENTITIES - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Carrying amount	[1]	$ 17,360		$ 17,370
Eliminations
Variable Interest Entity [Line Items]
Carrying amount		(7,511)		(7,696)
VIEs which are not primary beneficiary
Variable Interest Entity [Line Items]
Carrying amount		68		71
(Loss) income from equity method investments		$ (12)	$ (13)
Consolidated VIEs
Variable Interest Entity [Line Items]
Variable interest entities outsourcing agreement initial term		5 years
Carrying amount		$ 212		228
Consolidated VIEs | Eliminations
Variable Interest Entity [Line Items]
Liabilities associated with the certain outsourcing agreements and purchase options		$ 128		$ 127

[1] Our consolidated total assets as of March 31, 2020 and December 31, 2019 include total assets of variable interest entities (VIEs) of $212 million and $228 million, respectively, which can only be used to settle the obligations of the VIEs. Our consolidated total liabilities as of both March 31, 2020 and December 31, 2019 include total liabilities of VIEs of $27 million for which the creditors of the VIEs have no recourse to us. See Note 8. Variable Interest Entities.