SHAREHOLDERS' EQUITY - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	$ 2,151	$ 4,028	$ 2,630
Other comprehensive income loss before reclassifications net of tax	4,466	(2,150)	1,386
Amounts reclassified from accumulated other comprehensive income net of tax	(2)	47	12
Other comprehensive income (loss), net of tax	4,464	(2,103)	1,398
Balance, end of period	6,615	2,151	4,028
Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		(148)
Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		374
Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(1,847)	(1,750)	(1,983)
Other comprehensive income loss before reclassifications net of tax	224	228	233
Amounts reclassified from accumulated other comprehensive income net of tax	0	0	0
Other comprehensive income (loss), net of tax	224	228	233
Balance, end of period	(1,623)	(1,847)	(1,750)
Unrealized foreign currency translation gains (losses) | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		0
Unrealized foreign currency translation gains (losses) | Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		(325)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	4,234	5,964	4,805
Other comprehensive income loss before reclassifications net of tax	4,327	(2,350)	1,158
Amounts reclassified from accumulated other comprehensive income net of tax	(13)	34	1
Other comprehensive income (loss), net of tax	4,314	(2,316)	1,159
Balance, end of period	8,548	4,234	5,964
Unrealized gains (losses) on investment securities | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		(148)
Unrealized gains (losses) on investment securities | Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		734
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(24)	(23)	(24)
Other comprehensive income loss before reclassifications net of tax	(9)	2	1
Amounts reclassified from accumulated other comprehensive income net of tax	0	0	0
Other comprehensive income (loss), net of tax	(9)	2	1
Balance, end of period	(33)	(24)	(23)
Unrealized gains (losses) on derivatives | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		0
Unrealized gains (losses) on derivatives | Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		(3)
Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	(212)	(163)	(168)
Other comprehensive income loss before reclassifications net of tax	(76)	(30)	(6)
Amounts reclassified from accumulated other comprehensive income net of tax	11	13	11
Other comprehensive income (loss), net of tax	(65)	(17)	5
Balance, end of period	$ (277)	(212)	$ (163)
Pension liability adjustment | Accounting Standards Update 2016-01
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		0
Pension liability adjustment | Accounting Standards Update 2018-02
Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income net of tax		$ (32)