Segments and Geographic Information - Selected Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 15,524	$ 11,247
Total assets	64,539		$ 61,220
Total Long-lived assets	16,651		16,124
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	3,542	1,628
Total assets	21,233		21,683
Total Long-lived assets	396		523
Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	10,278	7,757
Total assets	4,916		1,366
Total Long-lived assets	536		535
Nottingham, UK Facility [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	793	949
Total assets	38,371		38,129
Total Long-lived assets	15,717		15,064
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	911	$ 913
Total assets	19		42
Total Long-lived assets	$ 2		$ 2