Long Term Obligations - Schedule of Payment Obligations (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Non-current portion of notes payable	$ 41,928	$ 48,298
Non-current portion of long term royalty-based debt	57,269	0
Royalty Based Debt \| HealthCare Royalty Partners and its Affiliates (“HCR”)
Debt Instrument [Line Items]
Less: interests to be accreted in future periods	(109,060)	(125,851)
Less: payments made	(6,006)	(816)
Less: current portion of royalties	(18,302)	(8,627)
Total repayment obligations	290,550	290,550
Carrying value of long term royalty-based debt	175,484	163,883
Non-current portion of long term royalty-based debt	157,182	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	(6,191)	(8,643)
Less: payments made	(3,564)	(497)
Carrying value of notes payable	52,745	53,360
Less: current portion of royalties	(10,817)	(5,062)
Non-current portion of notes payable	$ 41,928	$ 48,298

Interests to be accreted in future periods.

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Long term debt 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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