SHAREHOLDERS' EQUITY - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	$ 4,188	$ 4,481	$ 6,615	$ 2,151
Other comprehensive income (loss) before reclassifications net of tax	2,501	1,899	(835)	4,240
Amounts reclassified from accumulated other comprehensive income net of tax	61	(16)	122	(27)
Other comprehensive income (loss), net of tax	2,562	1,883	(713)	4,213
Balance, end of period	6,750	6,364	6,750	6,364
Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(1,543)	(1,848)	(1,623)	(1,847)
Other comprehensive income (loss) before reclassifications net of tax	74	393	154	392
Amounts reclassified from accumulated other comprehensive income net of tax	0	0	0	0
Other comprehensive income (loss), net of tax	74	393	154	392
Balance, end of period	(1,469)	(1,455)	(1,469)	(1,455)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	6,043	6,561	8,548	4,234
Other comprehensive income (loss) before reclassifications net of tax	2,433	1,512	(975)	3,853
Amounts reclassified from accumulated other comprehensive income net of tax	56	(18)	111	(32)
Other comprehensive income (loss), net of tax	2,489	1,494	(864)	3,821
Balance, end of period	8,532	8,055	8,532	8,055
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(35)	(26)	(33)	(24)
Other comprehensive income (loss) before reclassifications net of tax	(1)	(1)	(3)	(3)
Amounts reclassified from accumulated other comprehensive income net of tax	0	0	0	0
Other comprehensive income (loss), net of tax	(1)	(1)	(3)	(3)
Balance, end of period	(36)	(27)	(36)	(27)
Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(277)	(206)	(277)	(212)
Other comprehensive income (loss) before reclassifications net of tax	(5)	(5)	(11)	(2)
Amounts reclassified from accumulated other comprehensive income net of tax	5	2	11	5
Other comprehensive income (loss), net of tax	0	(3)	0	3
Balance, end of period	$ (277)	$ (209)	(277)	$ (209)
Cumulative effect, period of adoption, adjustment | Accounting Standards Update 2019-04
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			848
Cumulative effect, period of adoption, adjustment | Unrealized foreign currency translation gains (losses) | Accounting Standards Update 2019-04
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			0
Cumulative effect, period of adoption, adjustment | Unrealized gains (losses) on investment securities | Accounting Standards Update 2019-04
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			848
Cumulative effect, period of adoption, adjustment | Unrealized gains (losses) on derivatives | Accounting Standards Update 2019-04
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			0
Cumulative effect, period of adoption, adjustment | Pension liability adjustment | Accounting Standards Update 2019-04
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			0
Cumulative effect, period of adoption, adjusted balance
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			7,463
Cumulative effect, period of adoption, adjusted balance | Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			(1,623)
Cumulative effect, period of adoption, adjusted balance | Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			9,396
Cumulative effect, period of adoption, adjusted balance | Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			(33)
Cumulative effect, period of adoption, adjusted balance | Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period			$ (277)