Convertible debt issuance costs.

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Debt instrument repurchase price percentage.

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Line of credit facility prepayment fee percentage.

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Number of tranches.

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Purchase of capped call options.

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Voting rights percentage.

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

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Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

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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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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount, after accumulated amortization, of debt discount.

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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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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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The cap rate on a price risk derivative such as a cap or collar. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

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The strike price on the price risk option contract such as a put option or a call option.

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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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The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Carrying value as of the balance sheet date of loans payable (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

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The cash inflow from the issuance 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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The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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Indebtedness - Additional Information (Detail)			1 Months Ended	12 Months Ended
Indebtedness - Additional Information (Detail)	Dec. 13, 2019 USD ($) Tranch	Nov. 14, 2017 USD ($) shares $ / shares	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)
Debt Instrument [Line Items]
Debt instrument, face amount				$ 820,000,000
Proceeds for issuance of notes allocated to equity						$ 570,000,000
Amount paid for capped calls transactions						50,901,000
Prepayment fee percentage				2.00%
Line of credit facility, lenders fee				1.75%
Debt extinguishment loss			$ (2,300,000)		$ (2,322,000)
Long-term debt				$ 681,900,000	420,554,000
Convertible Debt, The Term Loan, The Revolver and The Mortgage Loans [Member]
Debt Instrument [Line Items]
Long-term debt				681,900,000
Interest expense related to debt facilities				30,700,000	33,700,000	$ 5,800,000
2024 Convertible Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 570,000,000.0		$ 570,000,000	$ 570,000,000
Debt instrument, maturity date		Nov. 15, 2024
Debt instrument, interest rate per annum		1.50%
Debt instrument, payment frequency				The 2024 Notes were issued at face value and bear interest at the rate of 1.50% per annum, payable semi-annually in cash on each May 15 and November 15, commencing on May 15, 2018.
Debt instrument, conversion rate		0.013621
Debt instrument, conversion price \| $ / shares		$ 73.42		$ 73.42
Proceeds for issuance of notes allocated to equity		$ 161,100,000
Offering costs		4,200,000
Debt issuance costs		$ 10,600,000
Effective interest rate percentage				6.90%	6.90%	6.90%
Capped calls strike price \| $ / shares		73.42
Capped calls cap price \| $ / shares		104.88
Amount paid for capped calls transactions		$ 50,900,000
Debt discount				$ 120,182,000	$ 140,206,000
Debt issuance costs				7,922,000	$ 9,240,000
Credit agreement interest rate per annum		1.50%
2024 Convertible Notes [Member] \| Fundamental Change [Member]
Debt Instrument [Line Items]
Debt instrument, repurchase price percentage		100.00%
2024 Convertible Notes [Member] \| Minimum [Member] \| Beneficial Owner [Member] \| Fundamental Change [Member]
Debt Instrument [Line Items]
Voting percentage		50.00%
2024 Convertible Notes [Member] \| Common Stock [Member]
Debt Instrument [Line Items]
Debt instrument, convertible into shares \| shares		7,763,552
Biopharma Credit PLC and Biopharma Credit Investments V (Master) LP [Member] \| December 2019 Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Dec. 20, 2023
Debt instrument, interest rate per annum	8.50%
Current borrowing capacity	$ 500,000,000.0
Number of tranches \| Tranch	2
Prepayment fee percentage	2.00%
Debt discount				9,400,000
Debt issuance costs				700,000
Proceeds after debt discount and issuance cost				$ 244,900,000
Credit agreement interest rate per annum	8.50%
Biopharma Credit PLC and Biopharma Credit Investments V (Master) LP [Member] \| December 2019 Term Loan [Member] \| Tranch A [Member]
Debt Instrument [Line Items]
Current borrowing capacity	$ 250,000,000.0
Line of credit facility, lenders fee	1.75%
Biopharma Credit PLC and Biopharma Credit Investments V (Master) LP [Member] \| December 2019 Term Loan [Member] \| Tranch B [Member]
Debt Instrument [Line Items]
Current borrowing capacity	$ 250,000,000.0
Line of credit facility, lenders fee	1.75%
Biopharma Credit PLC and Biopharma Credit Investments V (Master) LP [Member] \| Minimum [Member] \| December 2019 Term Loan [Member]
Debt Instrument [Line Items]
Prepayment fee percentage	1.00%
Biopharma Credit PLC and Biopharma Credit Investments V (Master) LP [Member] \| Maximum [Member] \| December 2019 Term Loan [Member]
Debt Instrument [Line Items]
Prepayment fee percentage	2.00%
MidCap Financial Amended and Restated Credit and Security Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate per annum							6.25%
Current borrowing capacity							$ 60,000,000.0
Credit agreement interest rate per annum							6.25%
MidCap Financial Amended and Restated Credit and Security Agreement [Member] \| Revolving Loan [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate per annum							3.95%
Current borrowing capacity							$ 40,000,000.0
Credit agreement interest rate per annum							3.95%