Acquisitions - Summary of Pro forma Financial Information (Detail) - INVISTA Aromatic Polyester Polyol Business Acquisition [Member] - 2021 Acquisitions [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Business Acquisition [Line Items]
Net Sales	$ 595,511	$ 480,949	$ 1,145,690	$ 956,836
Net Income Attributable to Stepan Company	$ 43,520	$ 34,723	$ 86,632	$ 63,325

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
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-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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-Name Accounting Standards Codification
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