Adjustments to Additional Paid in Capital, Repurchase of Convertible Debt

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Debt Conversion, Number of Shares of Common Stock Convertible per $1,000 of Principal Notes

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Debt Instrument, Convertible, Threshold Percentage Of Stock Price Trigger, Five Business Days

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Debt Instrument, Repurchased Amount, Accrued Interest

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Debt issuance costs, equity component

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Debt issuance costs, liability component

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Nonconvertible Debt Borrowing Rate at the Date of Issuance

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

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Carrying amount of long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months or greater than the normal operating cycle, if longer. The debt is convertible into another form of financial instrument, typically the entity's common stock.

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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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The price per share of the conversion feature embedded in the debt instrument.

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Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

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Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

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Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

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Face (par) amount of debt instrument at time of issuance.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Face (par) amount of the original debt instrument that was repurchased.

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

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Gross amount of debt extinguished.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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The cash outflow from the repayment of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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DEBT - Convertible Senior Notes Narrative (Details)			3 Months Ended
DEBT - Convertible Senior Notes Narrative (Details)	Jul. 24, 2020 USD ($) day $ / shares Rate shares	May 31, 2017 USD ($) day segment Rate	Mar. 31, 2021 USD ($) day segment Rate	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	May 31, 2017	May 31, 2017 shares	May 31, 2017 $ / shares	May 31, 2017 Rate
Debt Instrument [Line Items]
Annual interest rate on convertible senior notes	0.50%						0.625%
Amortization of convertible debt discount			$ 7,346,000		$ 3,111,000
Amortization of debt issuance costs			1,275,000		582,000
2025 Convertible Notes
Debt Instrument [Line Items]
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	12,000,000.0		10,505,000			$ 11,056,000
Debt issuance costs, equity component	$ 3,100,000
Interest expense			6,800,000
Interest expense recognized associated with the coupon rate			$ 700,000
Annual interest rate on convertible senior notes			0.50%
Amortization of convertible debt discount			$ 5,500,000
Amortization of debt issuance costs			600,000
Gross carrying amount			$ 575,000,000			575,000,000
2025 Convertible Notes \| Conversion option one
Debt Instrument [Line Items]
Conversion rate, sales price of common stock as a percentage of the conversion price \| Rate	130.00%		130.00%
Threshold trading days \| day	20
Threshold consecutive trading days \| day	30		30
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]
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		7,400,000	$ 1,074,000			1,297,000
Debt issuance costs, equity component		1,900,000
Interest expense			2,300,000		4,000,000.0
Interest expense recognized associated with the coupon rate			300,000		500,000
Annual interest rate on convertible senior notes							0.625%			0.625%
Amortization of convertible debt discount			1,800,000		3,100,000
Amortization of debt issuance costs			200,000		$ 400,000
Fair value			205,700,000
Gross carrying amount		$ 300,000,000.0	$ 169,659,000			$ 169,690,000
Repayments of convertible debt	$ 234,000,000.0
Debt repurchase amount	130,300,000
Debt repurchased amount, accrued interest	100,000
Extinguishment of debt	126,000,000.0
Reduction to additional paid-in capital, reacquisition of equity component	107,900,000
Loss on extinguishment of debt				$ 7,800,000
2022 Convertible Notes \| Conversion option one
Debt Instrument [Line Items]
Conversion rate, sales price of common stock as a percentage of the conversion price \| Rate		130.00%
Threshold trading days \| day		20	20
Threshold consecutive trading days \| segment		30	30
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	$ 575,000,000.0
Stated interest rate	0.50%
Fair value			$ 523,500,000
Convertible Debt \| 2025 Notes Under 13-day Purchase Option
Debt Instrument [Line Items]
Aggregate principal amount	$ 75,000,000.0