Segment Information (Revenue by Geographic Region) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 44,248	$ 15,724	$ 83,720	$ 35,374
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	21,322	7,646	40,292	19,080
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	17,097	3,010	32,481	6,035
Rest of the World
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 5,829	$ 5,068	$ 10,947	$ 10,259

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

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