Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 22,168	$ 21,853	$ 85,807	$ 81,661
Other comprehensive income :
Foreign currency translation adjustments (Note 10)	(2,534)	9,837	(28,776)	26,288
Defined benefit pension adjustments, net of tax (Note 10)	788	539	2,293	1,671
Derivative instrument activity, net of tax (Note 10)	(2)	(2)	(7)	(7)
Total other comprehensive income	(1,748)	10,374	(26,490)	27,952
Comprehensive income (loss)	20,420	32,227	59,317	109,613
Comprehensive (income) loss attributable to noncontrolling interests (Note 2)	31	20	55	(26)
Comprehensive income (loss) attributable to Stepan Company	$ 20,451	$ 32,247	$ 59,372	$ 109,587

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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