Investments in Associated Companies - Summarized Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity in net income of associated companies	$ 7,352	$ 5,064	$ 1,763
Korea Houghton Coporation [Member]
Equity in net income of associated companies	5,241	2,337	0
Equity Method Investee Name Nippon Quaker Japan [Member]
Equity in net income of associated companies	853	850	713
Equity Method Investee Name Kelko Panama [Member]
Equity in net income of associated companies	107	55	222
Equity Method Investee Name Kelko Venezuela [Member]
Equity in net income of associated companies	0	0	(138)
Equity Method Investee Name Primex [Member]
Equity in net income of associated companies	$ 1,151	$ 1,822	$ 966