Accounts Payable and Accrued Liabilities - Summary of Components of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accounts payable	$ 8,508	$ 12,236
Accrued rebates	9,296	5,648
Accrued compensation and benefits	2,770	3,472
Accrued acquisition costs	1,427	2,311
Accrued returns	658	915
Accrued royalties	562	488
Accrued clinical trial costs	348	234
Accrued legal	72	216
Accrued other	278	629
Total accounts payable and accrued liabilities	$ 23,919	$ 26,149