ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Accumulated Other Comprehensive (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 02, 2019	Jan. 01, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 20,817	$ 20,270	$ 19,747
Other comprehensive loss before reclassifications	604	(272)	(20)
Other-than-temporary impairment not recognized in earnings on debt securities	0	(3)	0
Amounts reclassified to the Consolidated Statements of Operations	76	(1)	13
Total other comprehensive income (loss), net of income taxes	680	(276)	(7)
Reclassification of tax effects resulting from the 2017 Tax Legislation			(145)
Cumulative effect of change in accounting standards				$ 17	$ 5
Ending balance	22,201	20,817	20,270
Net Unrealized (Losses) Gains on Derivatives before 2017-12 adoption
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(143)	(143)	(88)
Other comprehensive loss before reclassifications		(33)	(14)
Other-than-temporary impairment not recognized in earnings on debt securities		0
Amounts reclassified to the Consolidated Statements of Operations		33	(16)
Total other comprehensive income (loss), net of income taxes		0	(30)
Reclassification of tax effects resulting from the 2017 Tax Legislation			(25)
Ending balance		(143)	(143)
Net Unrealized (Losses) Gains on Derivatives
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive loss before reclassifications	103
Amounts reclassified to the Consolidated Statements of Operations	43
Total other comprehensive income (loss), net of income taxes	146
Cumulative effect of change in accounting standards					0
Ending balance	3
Net Unrealized (Losses) Gains on Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(490)	(236)	(186)
Other comprehensive loss before reclassifications	501	(239)	(6)
Other-than-temporary impairment not recognized in earnings on debt securities		(3)
Amounts reclassified to the Consolidated Statements of Operations	(15)	(12)	(2)
Total other comprehensive income (loss), net of income taxes	486	(254)	(8)
Reclassification of tax effects resulting from the 2017 Tax Legislation			(42)
Cumulative effect of change in accounting standards					5
Ending balance	1	(490)	(236)
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(463)	(441)	(394)
Other comprehensive loss before reclassifications	0	0	0
Other-than-temporary impairment not recognized in earnings on debt securities		0
Amounts reclassified to the Consolidated Statements of Operations	48	(22)	31
Total other comprehensive income (loss), net of income taxes	48	(22)	31
Reclassification of tax effects resulting from the 2017 Tax Legislation			(78)
Cumulative effect of change in accounting standards					$ 0
Ending balance	(415)	(463)	(441)
Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,096)	(820)	(668)
Total other comprehensive income (loss), net of income taxes	680	(276)	(7)
Reclassification of tax effects resulting from the 2017 Tax Legislation			(145)
Cumulative effect of change in accounting standards				$ 5
Ending balance	$ (411)	$ (1,096)	$ (820)