Accounts Payable and Accrued Liabilities - Summary of Components of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accounts payable	$ 2,672	$ 3,166
Accrued rebates	14,524	12,261
Accrued compensation and benefits	3,106	3,814
Accrued acquisition costs		318
Accrued returns	677	715
Accrued royalties	562	159
Accrued clinical trial costs		464
Accrued legal	382	70
Accrued regulatory expenses	537
Accrued other	1,024	572
Total accounts payable and accrued liabilities	$ 23,484	$ 21,539