Summary of Receivables and Deferred Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balances from contracts with customers only:
Accounts receivable	$ 43,045	$ 33,015
Deferred revenue (included in accrued liabilities in the consolidated balance sheets)	3,728
Revenue recognized during the six-month period relating to:
The beginning deferred revenue balance	$ 1,668

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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