FAIR VALUE MEASUREMENTS - Schedule of Assets Measured on Recurring Basis Level 3 Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Residential mortgages (2)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 893	$ 577	$ 658	$ 642
Issuances	122	86	209	153
Settlements	(47)	(46)	(105)	(86)
Change in fair value during the period	(66)	(49)	140	(331)
Ending balance	902	568	902	568
Other Derivative Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	38	143	197	19
Issuances	81	234	243	405
Settlements	(97)	(344)	(180)	(420)
Change in fair value during the period	67	140	(171)	169
Ending balance	$ 89	173	$ 89	173
Cumulative Effect, Period Of Adoption, Adjustment | Residential mortgages (2)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		0		190
Cumulative Effect, Period Of Adoption, Adjustment | Other Derivative Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		0		0
Cumulative Effect, Period Of Adoption, Adjusted Balance | Residential mortgages (2)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		577		832
Cumulative Effect, Period Of Adoption, Adjusted Balance | Other Derivative Contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 143		$ 19