DEBT - Convertible Senior Notes Narrative (Details)			3 Months Ended	9 Months Ended
	Jul. 24, 2020 USD ($) day $ / shares Rate shares	May 31, 2017 day segment Rate	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment day Rate	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	May 31, 2017 USD ($)	May 31, 2017 Rate	May 31, 2017 shares	May 31, 2017 $ / shares
Debt Instrument [Line Items]
Amortization of debt discount				$ 22,297,000	$ 12,429,000
Amortization of debt issuance costs				3,756,000	2,241,000
Repayments of convertible debt				$ 0	233,862,000
2025 Convertible Notes
Debt Instrument [Line Items]
Stated interest rate				0.50%		0.50%
Initial conversion rate, shares per $1,000 principal amount of notes | shares	2.1683
Initial conversion price per share (in dollars per share) | $ / shares	$ 461.19
Cash repurchase at a price equal to the principal amount of the notes, percentage | Rate	100.00%
Nonconvertible debt borrowing rate at the date of issuance | Rate	5.30%
Debt component of the principal amount	$ 455,600,000
Equity component of the principal amount	119,400,000
Financing costs	15,100,000
Debt issuance costs	12,000,000			$ 9,418,000		$ 11,056,000
Debt issuance costs, equity component	$ 3,100,000
Interest expense				20,300,000	4,900,000
Interest expense recognized associated with the coupon rate				$ 2,200,000	$ 500,000
Annual interest rate on convertible senior notes			0.50%	0.50%	0.50%
Amortization of debt discount				$ 16,400,000	$ 4,000,000
Amortization of debt issuance costs				1,700,000	400,000
Gross carrying amount				$ 575,000,000		$ 575,000,000
2025 Convertible Notes | Conversion option one
Debt Instrument [Line Items]
Threshold trading days | day	20
Threshold consecutive trading days | day	30			30
Conversion rate, sales price of common stock as a percentage of the conversion price | Rate	130.00%			130.00%
2025 Convertible Notes | Conversion option two
Debt Instrument [Line Items]
Threshold trading days | day	5
Threshold consecutive trading days | day	5
Conversion rate | Rate	98.00%
2022 Convertible Notes
Debt Instrument [Line Items]
Stated interest rate				0.625%		0.625%
Initial conversion rate, shares per $1,000 principal amount of notes | shares									4.8163
Initial conversion price per share (in dollars per share) | $ / shares										$ 207.63
Cash repurchase at a price equal to the principal amount of the notes, percentage | Rate		100.00%
Nonconvertible debt borrowing rate at the date of issuance		5.36%
Debt component of the principal amount							$ 238,400,000
Equity component of the principal amount							61,600,000
Financing costs							9,300,000
Debt issuance costs				$ 621,000		$ 1,297,000	7,400,000
Debt issuance costs, equity component							1,900,000
Interest expense				7,100,000	10,700,000
Interest expense recognized associated with the coupon rate				800,000	1,300,000
Annual interest rate on convertible senior notes		0.625%						0.625%
Amortization of debt discount				5,600,000	8,400,000
Amortization of debt issuance costs				700,000	$ 1,000,000
Fair value				167,300,000
Gross carrying amount				$ 169,659,000		$ 169,690,000	$ 300,000,000
Repayments of convertible debt	$ 234,000,000
Debt repurchase amount	130,300,000
Debt repurchased amount, accrued interest	100,000
Extinguishment of debt	126,000,000
Repurchase of 0.625% Convertible Senior Notes, net	107,900,000		$ (107,882,000)
Loss on extinguishment of debt			$ 7,800,000
2022 Convertible Notes | Conversion option one
Debt Instrument [Line Items]
Threshold trading days | day		20		20
Threshold consecutive trading days | segment		30		30
Conversion rate, sales price of common stock as a percentage of the conversion price | Rate		130.00%
2022 Convertible Notes | Conversion option two
Debt Instrument [Line Items]
Threshold trading days | day		5
Threshold consecutive trading days | day		5
Conversion rate | Rate		98.00%
Convertible Debt | 2025 Convertible Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 575,000,000
Stated interest rate	0.50%					0.50%
Fair value				$ 500,500,000
Convertible Debt | 2025 Notes Under 13-day Purchase Option
Debt Instrument [Line Items]
Aggregate principal amount	$ 75,000,000
Convertible Debt | 2022 Convertible Notes
Debt Instrument [Line Items]
Stated interest rate		0.625%				0.625%