ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 22,673	$ 22,201	$ 20,817
Other comprehensive income (loss) before reclassifications	(577)	479	604
Amounts reclassified to the Consolidated Statements of Operations	(28)	(128)	76
Total other comprehensive income (loss), net of income taxes	(605)	351	680
Ending balance	23,420	22,673	22,201
Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(60)	(411)	(1,096)
Total other comprehensive income (loss), net of income taxes	(605)	351	680
Ending balance	(665)	(60)	(411)
Net Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(11)	3	(143)
Other comprehensive income (loss) before reclassifications	(49)	97	103
Amounts reclassified to the Consolidated Statements of Operations	(101)	(111)	43
Total other comprehensive income (loss), net of income taxes	(150)	(14)	146
Ending balance	(161)	(11)	3
Net Unrealized Gains (Losses) on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	380	1	(490)
Other comprehensive income (loss) before reclassifications	(528)	382	501
Amounts reclassified to the Consolidated Statements of Operations	(8)	(3)	(15)
Total other comprehensive income (loss), net of income taxes	(536)	379	486
Ending balance	(156)	380	1
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(429)	(415)	(463)
Other comprehensive income (loss) before reclassifications	0	0	0
Amounts reclassified to the Consolidated Statements of Operations	81	(14)	48
Total other comprehensive income (loss), net of income taxes	81	(14)	48
Ending balance	$ (348)	(429)	(415)
Cumulative Effect, Period of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		(331)	17
Ending balance			(331)
Cumulative Effect, Period of Adoption, Adjustment | Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		5	5
Ending balance			5
Cumulative Effect, Period of Adoption, Adjustment | Net Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		0
Ending balance			0
Cumulative Effect, Period of Adoption, Adjustment | Net Unrealized Gains (Losses) on Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		5
Ending balance			5
Cumulative Effect, Period of Adoption, Adjustment | Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance		$ 0
Ending balance			$ 0