SHARE-BASED COMPENSATION - Summary of Share-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Components and classification of share-based compensation expense
Share-based compensation expense	$ 27	$ 27	$ 54	$ 51
Research and development expenses
Components and classification of share-based compensation expense
Share-based compensation expense	3	3	6	5
Selling, general and administrative expenses
Components and classification of share-based compensation expense
Share-based compensation expense	24	24	48	46
Stock options
Components and classification of share-based compensation expense
Share-based compensation expense	4	6	8	12
RSUs
Components and classification of share-based compensation expense
Share-based compensation expense	$ 23	$ 21	$ 46	$ 39