Segments and Geographic Information - Selected Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 15,310	$ 13,956	$ 30,834	$ 25,203
Total assets	67,768		67,768		$ 61,220
Total Long-lived assets	17,734		17,734		16,124
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	3,917	2,387	7,459	4,015
Total assets	20,886		20,886		21,683
Total Long-lived assets	345		345		523
Switzerland [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	9,518	9,759	19,796	17,516
Total assets	7,362		7,362		1,366
Total Long-lived assets	1,257		1,257		535
Nottingham, UK Facility [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	1,182	1,088	1,975	2,037
Total assets	39,491		39,491		38,129
Total Long-lived assets	16,129		16,129		15,064
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	693	$ 722	1,604	$ 1,635
Total assets	29		29		42
Total Long-lived assets	$ 3		$ 3		$ 2