Operating Segment and Enterprise Wide Reporting - Schedule of Net Long-lived Tangible Assets by Location (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Revenues From External Customers And Long Lived Assets [Line Items]
Net long-lived tangible assets	$ 27,032	$ 29,937
United States [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Net long-lived tangible assets	24,645	26,709
United Kingdom [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Net long-lived tangible assets	261	578
Europe (Excluding United Kingdom) [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Net long-lived tangible assets	78	97
Asia Pacific [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Net long-lived tangible assets	$ 2,048	$ 2,553