Accounts Receivable and Reserves for Product Sales - Summary of Change in Reserves for Discounts and Allowances (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Balance, as of December 31, 2016	$ 306
Provision	8,880
Payments/credits	(4,634)
Balance, as of September 30, 2017	4,552
Chargebacks [Member]
Accounts Notes And Loans Receivable [Line Items]
Balance, as of December 31, 2016	1
Provision	3,760
Payments/credits	(3,330)
Balance, as of September 30, 2017	431
Rebates [Member]
Accounts Notes And Loans Receivable [Line Items]
Balance, as of December 31, 2016	238
Provision	4,270
Payments/credits	(660)
Balance, as of September 30, 2017	3,848
Prompt Pay [Member]
Accounts Notes And Loans Receivable [Line Items]
Provision	78
Payments/credits	(52)
Balance, as of September 30, 2017	26
Other Accruals [Member]
Accounts Notes And Loans Receivable [Line Items]
Balance, as of December 31, 2016	67
Provision	772
Payments/credits	(592)
Balance, as of September 30, 2017	$ 247