Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Information about Geographic Areas - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) sales_force Segment	Jun. 30, 2017 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of sales forces \| sales_force			1
Number of reportable segment \| Segment			1
Total revenue	$ 24,999	$ 34,592	$ 48,084	$ 52,656
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 15,900	$ 26,800