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		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument
Amortization of debt discount and debt issuance costs			$ 30	$ 33
Convertible Debt
Debt Instrument
Coupon interest expense	$ 4	$ 4	8	7
Amortization of debt discount and debt issuance costs	10	17	24	29
Total interest expense	$ 14	$ 21	$ 32	$ 36
Weighted-average effective interest rate	3.50%	3.20%	3.70%	3.30%
Senior Notes
Debt Instrument
Coupon interest expense	$ 60	$ 70	$ 138	$ 110
Amortization of debt discount and debt issuance costs	4	2	6	4
Total interest expense	$ 64	$ 72	$ 144	$ 114