SHAREHOLDERS' EQUITY - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	$ 2,630	$ 625	$ 1,979
Other comprehensive income loss before reclassifications net of tax	[1]	1,386	2,037	(1,314)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	12	(32)	(40)
Other comprehensive income (loss), net of income taxes	[1]	1,398	2,005	(1,354)
Balance, end of period	[1]	4,028	2,630	625
Unrealized foreign currency translation gains (losses)
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(1,983)	(2,196)	(2,541)
Other comprehensive income loss before reclassifications net of tax	[1]	233	213	345
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	0	0	0
Other comprehensive income (loss), net of income taxes	[1]	233	213	345
Balance, end of period	[1]	(1,750)	(1,983)	(2,196)
Unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	4,805	2,986	4,672
Other comprehensive income loss before reclassifications net of tax	[1]	1,158	1,854	(1,646)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	1	(35)	(40)
Other comprehensive income (loss), net of income taxes	[1]	1,159	1,819	(1,686)
Balance, end of period	[1]	5,964	4,805	2,986
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(24)	(26)	(26)
Other comprehensive income loss before reclassifications net of tax	[1]	1	2	0
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	0	0	0
Other comprehensive income (loss), net of income taxes	[1]	1	2	0
Balance, end of period	[1]	(23)	(24)	(26)
Pension liability adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Balance, beginning of period	[1]	(168)	(139)	(126)
Other comprehensive income loss before reclassifications net of tax	[1]	(6)	(32)	(13)
Amounts reclassified from accumulated other comprehensive income net of tax	[1]	11	3	0
Other comprehensive income (loss), net of income taxes	[1]	5	(29)	(13)
Balance, end of period	[1]	$ (163)	$ (168)	$ (139)

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