CONVERTIBLE DEBT - Schedule of Convertible Note Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Feb. 29, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Convertible notes, net, current portion	$ (255,464)		$ 0
Net long-term convertible debt	$ 1,320,760		803,605
2028 Convertible notes
Debt Instrument [Line Items]
Interest rate (as a percent)	0.375%	0.375%
Effective interest rate (as a percent)	5.20%
Fair value of liability component at issuance	$ 790,608
Convertible notes payable, gross	1,150,000		0
Less: Debt discount	(328,372)		0
Less: Debt issuance costs	(15,041)		0
Unamortized discount	328,372		0
Debt issuance costs	$ 15,041		0
2027 Convertible notes
Debt Instrument [Line Items]
Interest rate (as a percent)	0.375%
Effective interest rate (as a percent)	6.30%
Fair value of liability component at issuance	$ 472,501
Convertible notes payable, gross	747,500		747,500
Less: Debt discount	(224,517)		(253,340)
Less: Debt issuance costs	(8,810)		(10,251)
Unamortized discount	224,517		253,340
Debt issuance costs	$ 8,810		10,251
2025 Convertible notes
Debt Instrument [Line Items]
Interest rate (as a percent)	1.00%
Effective interest rate (as a percent)	6.00%
Fair value of liability component at issuance	$ 227,103
Convertible notes payable, gross	315,049		415,049
Less: Debt discount	(55,796)		(89,123)
Less: Debt issuance costs	(3,789)		(6,230)
Fair value of liability component of 2025 notes	654,800
Carrying amount of equity component of 2025 notes	267,900
Unamortized discount	55,796		89,123
Debt issuance costs	3,789		6,230
Aggregate Convertible Notes
Debt Instrument [Line Items]
Convertible notes payable, gross	2,212,549		1,162,549
Less: Debt discount	(608,685)		(342,463)
Less: Debt issuance costs	(27,640)		(16,481)
Net convertible debt including current maturities	1,576,224		803,605
Convertible notes, net, current portion	(255,464)		0
Net long-term convertible debt	1,320,760		803,605
Unamortized discount	608,685		342,463
Debt issuance costs	$ 27,640		$ 16,481

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Debt Instrument, Convertible, Amount of Liability Component at Issuance

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Debt Instrument, Convertible, Fair Value of Liability Component

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Carrying value as of the balance sheet date of long-term debt (with maturities initially due after one year or beyond the operating cycle if longer) identified as Convertible Notes Payable, excluding current portion. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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Carrying value as of the balance sheet date of the portion of long-term debt due within one year or the operating cycle if longer identified as Convertible Notes Payable. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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