FAIR VALUE MEASUREMENT - Level 3 Fair Value Rollforward Narrative (Details) - Long-term debt - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair value, assets and liabilities measured on recurring basis, level 3 fair-value category disclosures
Transfers into Level 3, liabilities	$ 747	$ 815	$ 1,624	$ 1,755
Transfers out of Level 3, liabilities	$ 1,360	$ 540	$ 2,961	$ 1,304