SHAREHOLDERS' EQUITY - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	$ 4,028		$ 2,630
Other comprehensive income loss before reclassifications net of tax	[1]	(571)		(10)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	228		12
Other comprehensive income (loss), net of tax	[1]	(343)		2
Balance, end of period	[1]	3,685		2,632
Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(1,750)		(1,983)
Other comprehensive income loss before reclassifications net of tax	[1]	447		333
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	0		0
Other comprehensive income (loss), net of tax	[1]	447		333
Balance, end of period	[1]	(1,303)		(1,650)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	5,964		4,805
Other comprehensive income loss before reclassifications net of tax	[1]	(983)		(341)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	225	[2]	10
Other comprehensive income (loss), net of tax	[1]	(758)		(331)
Balance, end of period	[1]	5,206		4,474
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(23)		(24)
Other comprehensive income loss before reclassifications net of tax	[1]	2		2
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	0		0
Other comprehensive income (loss), net of tax	[1]	2		2
Balance, end of period	[1]	(21)		(22)
Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(163)		(168)
Other comprehensive income loss before reclassifications net of tax	[1]	(37)		(4)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	3		2
Other comprehensive income (loss), net of tax	[1]	(34)		(2)
Balance, end of period	[1]	(197)		(170)
Accounting Standards Update 2016-01 | Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes	[3]	(148)		0
Accounting Standards Update 2018-02 | Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes	[3]	$ 374		$ 0

[1] All amounts in the table above are net of tax.

[2] Includes amounts reclassified due to changes in accounting principles of $(148) related to financial instruments and $374 related to tax effects from tax reform

[3] See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018.