ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 01, 2020	Jan. 01, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 21,950	$ 21,531	$ 22,201	$ 20,817
Other comprehensive income before reclassifications	41	289	537	574
Other-than-temporary impairment not recognized in earnings on debt securities	0	1	0	1
Amounts reclassified to the Consolidated Statements of Operations	(32)	15	(32)	28
Net other comprehensive income	9	305	505	603
Cumulative effect of change in accounting principle					$ (331)	$ 17
Ending balance	22,418	22,017	22,418	22,017
Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	85	(793)	(411)	(1,096)
Net other comprehensive income	9	305	505	603
Cumulative effect of change in accounting principle					$ 0	5
Ending balance	94	(488)	94	(488)
Net Unrealized (Losses) Gains on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	96	(89)	3	(143)
Other comprehensive income before reclassifications	(8)	68	88	107
Other-than-temporary impairment not recognized in earnings on debt securities		0		0
Amounts reclassified to the Consolidated Statements of Operations	(34)	15	(37)	30
Net other comprehensive income	(42)	83	51	137
Cumulative effect of change in accounting principle						0
Ending balance	54	(6)	54	(6)
Net Unrealized (Losses) Gains on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	401	(244)	1	(490)
Other comprehensive income before reclassifications	49	221	449	467
Other-than-temporary impairment not recognized in earnings on debt securities		1		1
Amounts reclassified to the Consolidated Statements of Operations	(2)	(3)	(2)	(8)
Net other comprehensive income	47	219	447	460
Cumulative effect of change in accounting principle						5
Ending balance	448	(25)	448	(25)
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(412)	(460)	(415)	(463)
Other comprehensive income before reclassifications	0	0	0	0
Other-than-temporary impairment not recognized in earnings on debt securities		0		0
Amounts reclassified to the Consolidated Statements of Operations	4	3	7	6
Net other comprehensive income	4	3	7	6
Cumulative effect of change in accounting principle						$ 0
Ending balance	$ (408)	$ (457)	$ (408)	$ (457)

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 of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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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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