Summary of Receivables and Deferred Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Balances from contracts with customers only:
Accounts receivable	$ 41,968	$ 33,015
Deferred revenue (included in accrued liabilities in the consolidated balance sheets)	4,286
Revenue recognized during the nine-month period ending September 30, 2019 relating to:
The beginning deferred revenue balance	$ 2,768

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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