Segment Information and Geographic Data - Additional Information (Detail) - segment	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Reportable segments	2
Customer A | Customer Concentration Risk | Accounts Receivable
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration risk percentage	23.00%	19.50%
Customer B | Customer Concentration Risk | Accounts Receivable
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration risk percentage	16.90%	14.00%
Customer C | Customer Concentration Risk | Accounts Receivable
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration risk percentage	14.60%	11.70%