INCOME TAXES - Income Tax Expense Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended					6 Months Ended		12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Expense Reconciliation
Income tax expense at U.S. statutory rate								$ 204	$ 340	$ 383
Tax incentives								(140)	(161)	(139)
State and local taxes, net of federal benefit								(17)	5	(6)
Impact of foreign taxes								65	122	(41)
Swiss tax reform net asset basis step-up								(159)	0	0
Deferred tax revaluation due to 2017 Tax Act and foreign tax reform								(19)	(8)	(283)
Transition tax due to 2017 Tax Act								(16)	(5)	529
U.S. valuation allowance due to 2017 Tax Act								0	(194)	339
Other valuation allowances			$ 21					110	21	(6)
Stock compensation windfall tax benefits								(54)	(40)	(56)
Foreign tax credits								0	0	(246)
Research and development tax credits								(13)	(17)	(5)
Other, net								(2)	2	22
Income tax expense (benefit)	$ 13	$ 44	$ 102	$ 63	$ 46	$ 57	$ 109	$ (41)	$ 65	$ 491