RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 20,817	$ 20,270
Other comprehensive loss before reclassifications	285	(324)
Other-than-temporary impairment not recognized in earnings on debt securities	0	(1)
Amounts reclassified to the Consolidated Statements of Operations	13	0
Cumulative effect of change in accounting standards			$ 17
Net other comprehensive (loss) income	303	(325)
Ending balance	21,531	20,059
Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,096)	(820)
Cumulative effect of change in accounting standards			5
Ending balance	(793)	(1,145)
Net Unrealized (Losses) Gains on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(143)	(143)
Other comprehensive loss before reclassifications	39	(52)
Other-than-temporary impairment not recognized in earnings on debt securities	0	0
Amounts reclassified to the Consolidated Statements of Operations	15	2
Cumulative effect of change in accounting standards			0
Net other comprehensive (loss) income	54	(50)
Ending balance	(89)	(193)
Net Unrealized (Losses) Gains on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(490)	(236)
Other comprehensive loss before reclassifications	246	(272)
Other-than-temporary impairment not recognized in earnings on debt securities	0	(1)
Amounts reclassified to the Consolidated Statements of Operations	(5)	(5)
Cumulative effect of change in accounting standards			5
Net other comprehensive (loss) income	246	(278)
Ending balance	(244)	(514)
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(463)	(441)
Other comprehensive loss before reclassifications	0	0
Other-than-temporary impairment not recognized in earnings on debt securities	0	0
Amounts reclassified to the Consolidated Statements of Operations	3	3
Cumulative effect of change in accounting standards			$ 0
Net other comprehensive (loss) income	3	3
Ending balance	$ (460)	$ (438)

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 and reclassification adjustments of other comprehensive income (loss).

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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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