Segment Information (Long-Lived Assets by Geographic Region) (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 23,639	$ 27,183
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	15,426	18,318
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	7,159	7,638
Rest of the World
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 1,054	$ 1,227