Long Term Obligations - Schedule of Payment Obligations (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Notes payable, less current portion	$ 46,860	$ 48,298
Long term debt	56,839
Royalty Based Debt \| HealthCare Royalty Partners and its Affiliates (“HCR”)
Debt Instrument [Line Items]
Less: interests to be accreted in future periods	(120,431)	(125,851)
Less: payments made	(2,001)	(816)
Less: current portion of royalties	(11,192)	(8,627)
Total repayment obligations	290,550	290,550
Carrying value of long term royalty-based debt	168,118	163,883
Long term debt	156,926	155,256
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") \| Promissory Notes
Debt Instrument [Line Items]
Total repayment obligations	62,500	62,500
Less: interests to be accreted in future periods	(7,828)	(8,643)
Less: payments made	(1,198)	(497)
Carrying value of notes payable	53,474	53,360
Less: current portion of royalties	(6,614)	(5,062)
Notes payable, less current portion	$ 46,860	$ 48,298

Interests to be accreted in future periods.

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Long term debt repayment obligation.

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Notes payable repayment obligation.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Sum of the carrying values as of the balance sheet date of the portions of long-term notes payable due within one year or the operating cycle if longer.

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