Business Combination, Goodwill and Intangible Assets - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consideration:
Cash consideration paid		$ 0	$ 36,571	$ 0
Goodwill, Acquired During Period		$ 23,014
Société du Noir d'Acétylène de l'Aubette, SAS
Assets
Cash	$ 213
Other current assets	176
Accounts receivables	1,578
Inventories	924
Property, plant and equipment	5,317
Intangible assets	12,766
Total assets acquired	20,974
Liabilities
Current liabilities	2,488
Deferred tax liabilities	4,716
Total liabilities assumed	7,204
Net assets acquired	13,770
Consideration:
Cash consideration paid	$ 36,784