Significant Accounting Policies - Summary of Impact of Accounts Receivable Reserves on Gross Trade Accounts Receivable Balances (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross trade accounts receivable	$ 133,531	$ 86,133
Accounts receivable, net	103,583	66,523
Trade Allowances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation allowances and reserves	(27,947)	(19,495)
Chargebacks
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation allowances and reserves	$ (2,001)	$ (115)