DEBT - Summary of Interest Expenses and Weighted-Average Effective Interest Rates Related To Convertible Senior Notes and Other Senior Notes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument
Amortization of debt discount and debt issuance costs			$ 44	$ 48
Convertible Debt
Debt Instrument
Coupon interest expense	$ 3	$ 4	11	11
Amortization of debt discount and debt issuance costs	12	13	36	42
Total interest expense	$ 15	$ 17	$ 47	$ 53
Weighted-average effective interest rate	3.90%	3.90%	3.70%	3.50%
Senior Notes
Debt Instrument
Coupon interest expense	$ 60	$ 77	$ 198	$ 187
Amortization of debt discount and debt issuance costs	2	2	8	6
Total interest expense	$ 62	$ 79	$ 206	$ 193