Segment Information - Long-Lived Assets by Geographic Region (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 7,632	$ 7,183
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	5,237	5,424
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 2,395	$ 1,759