Segment Information - Long-Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	$ 105,437	$ 104,085
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	101,051	98,683
International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	$ 4,386	$ 5,402