Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 33,342	$ 25,880	$ 96,724	$ 81,068
Other comprehensive income:
Foreign currency translation adjustments (Note 11)	[1]	8,631	(19,287)	(29,025)	(11,290)
Defined benefit pension adjustments, net of tax (Note 11)		839	473	2,455	1,558
Derivative instrument activity, net of tax (Note 11)		(3)	(2)	(7)	(6)
Total other comprehensive income		9,467	(18,816)	(26,577)	(9,738)
Comprehensive income		42,809	7,064	70,147	71,330
Comprehensive income attributable to noncontrolling interests (Note 2)		(211)	41	(330)	62
Comprehensive income attributable to Stepan Company		$ 42,598	$ 7,105	$ 69,817	$ 71,392

[1] Includes foreign currency translation adjustments related to noncontrolling interest.