Accounts Payable and Accrued Liabilities - Summary of Components of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable	$ 12,236	$ 9,397
Accrued rebates	5,648	3,842
Accrued compensation and benefits	3,472	2,052
Accrued acquisition costs	2,311
Accrued returns	915
Accrued royalties	488	518
Accrued clinical trial costs	234	615
Accrued legal	216	490
Accrued manufacturing costs		200
Accrued sales and marketing costs		193
Accrued other	629	265
Total accounts payable and accrued expenses	$ 26,149	$ 17,572