Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 47,210	$ 4,004
Accrued liabilities to related party	444	272
Astellas [Member] \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	100,000	20,100	$ 31,300
Expense related to collaboration agreements	1,500	1,000	$ 6,400
Accounts receivable from related party	47,200	4,000
Accrued liabilities to related party	400	$ 300
API Shipment [Member] \| Astellas [Member] \| Astellas Agreement [Member]
Related Party Transaction [Line Items]
Accrued liabilities to related party	43,800
Product Revenue [Member] \| API Shipment [Member] \| Astellas [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	$ 64,800

Amount of receivables arising from transactions with related parties due within one year or the normal operating cycle, if longer.

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Carrying amount as of the balance sheet date of obligations due all related parties. For classified balance sheets, represents the current portion of such liabilities (due within one year or within the normal operating cycle if longer).

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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