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
	Mar. 31, 2021	Mar. 31, 2020
Debt Instrument
Amortization of debt discount and debt issuance costs	$ 16	$ 14
Convertible Debt
Debt Instrument
Coupon interest expense	4	3
Amortization of debt discount and debt issuance costs	14	12
Total interest expenses	$ 18	$ 15
Weighted-average effective interest rate	3.90%	3.20%
Senior Notes
Debt Instrument
Coupon interest expense	$ 78	$ 40
Amortization of debt discount and debt issuance costs	2	2
Total interest expenses	$ 80	$ 42