Goodwill, In-Process Research and Development and Intellectual Property - Summary of Gross Intellectual Property, Accumulated Amortization, and Net Intellectual Property (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Developed Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 66,413	$ 66,413
Accumulated Amortization	(33,151)	(30,550)
Foreign currency translation impact	2,720	3,495
Net Carrying Amount	35,982	39,358
Technology and Patents Purchased [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	400	400
Accumulated Amortization	(82)	(72)
Foreign currency translation impact	22	30
Net Carrying Amount	340	358
Intellectual Property [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	66,813	66,813
Accumulated Amortization	(33,233)	(30,622)
Foreign currency translation impact	2,742	3,525
Net Carrying Amount	$ 36,322	$ 39,716