SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	Mar. 31, 2020	Jan. 01, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to accumulated deficit	$ 546	$ 1,136	$ 790		$ 2,688	$ 2,779	$ 2,815
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to accumulated deficit		$ (1)
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to accumulated deficit	$ (7,931)	(7,452)	$ (7,605)		$ (5,887)	$ (5,716)	$ (5,664)
Accumulated Deficit | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to accumulated deficit		$ (1)		$ 1