Revenue - Cumulative Effect of Changes to Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 80,656		$ 67,287
Prepaid expenses and other current assets	6,621		6,463
Accumulated other comprehensive loss	(1,077)		(1,242)
Accumulated deficit	(306,082)		$ (257,844)
ASC 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		$ 68,734
Prepaid expenses and other current assets		5,987
Accumulated other comprehensive loss		(1,238)
Accumulated deficit		(256,877)
Adjustments Due to ASC 606 [Member] \| ASC 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	2,514	1,447
Prepaid expenses and other current assets	$ (893)	(476)
Accumulated other comprehensive loss		4
Accumulated deficit		$ 967

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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