ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 22,418	$ 22,017	$ 22,201	$ 20,817
Other comprehensive income before reclassifications	(44)	38	493	612
Other-than-temporary impairment not recognized in earnings on debt securities	0	(1)	0	0
Amounts reclassified to the Consolidated Statements of Operations	(40)	11	(72)	39
Net other comprehensive income	(84)	48	421	651
Ending balance	22,469	21,851	22,469	21,851
Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	94	(488)	(411)	(1,096)
Net other comprehensive income	(84)	48	421	651
Ending balance	10	(440)	10	(440)
Net Unrealized (Losses) Gains on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	54	(6)	3	(143)
Other comprehensive income before reclassifications	0	(4)	88	103
Other-than-temporary impairment not recognized in earnings on debt securities		0
Amounts reclassified to the Consolidated Statements of Operations	(42)	10	(79)	40
Net other comprehensive income	(42)	6	9	143
Ending balance	12	0	12	0
Net Unrealized (Losses) Gains on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	448	(25)	1	(490)
Other comprehensive income before reclassifications	(44)	42	405	509
Other-than-temporary impairment not recognized in earnings on debt securities		(1)
Amounts reclassified to the Consolidated Statements of Operations	(1)	(2)	(3)	(10)
Net other comprehensive income	(45)	39	402	499
Ending balance	403	14	403	14
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(408)	(457)	(415)	(463)
Other comprehensive income before reclassifications	0	0	0	0
Other-than-temporary impairment not recognized in earnings on debt securities		0
Amounts reclassified to the Consolidated Statements of Operations	3	3	10	9
Net other comprehensive income	3	3	10	9
Ending balance	(405)	(454)	(405)	(454)
Cumulative Effect, Period Of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Ending balance	(331)	17	(331)	17
Cumulative Effect, Period Of Adoption, Adjustment \| Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance				5
Ending balance	$ 0	$ 5	$ 0	5
Cumulative Effect, Period Of Adoption, Adjustment \| Net Unrealized (Losses) Gains on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance				0
Cumulative Effect, Period Of Adoption, Adjustment \| Net Unrealized (Losses) Gains on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance				5
Cumulative Effect, Period Of Adoption, Adjustment \| Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance				$ 0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of other than temporary impairment loss (OTTI) on investments in available-for-sale and held-to-maturity debt securities, recognized in other comprehensive loss and attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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