Segment Information - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Description of customer revenue accounted for more than 10% of consolidated revenue		No single customer accounted for more than 10% of the Company's consolidated revenues during the three and six months ended June 30, 2018 and 2017.
Geographic Concentration Risk [Member]
Segment Reporting Information [Line Items]
Description of customer revenue accounted for more than 10% of consolidated revenue		No other country outside the United States and the United Kingdom accounted for more than 10% of the Company's consolidated revenues during the three and six months ended June 30, 2017. No other country outside the United States accounted for more than 10% of the Company's consolidated revenues during the three and six months ended June 30, 2018.
Geographic Concentration Risk [Member] | Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Percentage of revenues attributable to customers	11.40%		11.40%