SHAREHOLDERS' EQUITY - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	$ 8,934	$ 6,615
Other comprehensive income (loss) before reclassifications net of tax	(2,151)	(3,287)
Amounts reclassified from accumulated other comprehensive income net of tax	24	12
Other comprehensive income (loss), net of tax	(2,127)	(3,275)
Balance, end of period	6,807	4,188
Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(1,109)	(1,623)
Other comprehensive income (loss) before reclassifications net of tax	(565)	80
Amounts reclassified from accumulated other comprehensive income net of tax	0	0
Other comprehensive income (loss), net of tax	(565)	80
Balance, end of period	(1,674)	(1,543)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	10,361	8,548
Other comprehensive income (loss) before reclassifications net of tax	(1,583)	(3,359)
Amounts reclassified from accumulated other comprehensive income net of tax	16	6
Other comprehensive income (loss), net of tax	(1,567)	(3,353)
Balance, end of period	8,794	6,043
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(34)	(33)
Other comprehensive income (loss) before reclassifications net of tax	1	(2)
Amounts reclassified from accumulated other comprehensive income net of tax	0	0
Other comprehensive income (loss), net of tax	1	(2)
Balance, end of period	(33)	(35)
Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(284)	(277)
Other comprehensive income (loss) before reclassifications net of tax	(4)	(6)
Amounts reclassified from accumulated other comprehensive income net of tax	8	6
Other comprehensive income (loss), net of tax	4	0
Balance, end of period	$ (280)	(277)
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)