STOCKHOLDERS' EQUITY STOCKHOLDERS' EQUITY - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Jan. 01, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ (17)	$ (14)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	28,146	27,971	$ 27,969
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(13)	334
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	115	149
Other Comprehensive Income (Loss), Net of Tax	102	483
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(18)	6
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	16	(8)		$ (51)		$ 17
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	68	(26)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(1)	1
Other Comprehensive Income (Loss), Net of Tax	67	(25)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(1)	5
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(1,844)	(1,105)		(1,813)		(1,481)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(13)	376
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(18)	0
Other Comprehensive Income (Loss), Net of Tax	(31)	376
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(25)	(28)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(7,824)	(6,872)		(7,965)		(6,998)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	141	126
Other Comprehensive Income (Loss), Net of Tax	141	126
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	27	3
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(131)	(103)		(56)		(109)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(68)	(16)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(7)	22
Other Comprehensive Income (Loss), Net of Tax	(75)	6
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(9,783)	(8,088)	$ (9,885)	$ (9,885)	$ (8,591)	$ (8,571)
Other Comprehensive Income (Loss), Net of Tax	$ 102	$ 483