Sales of Assets - Additional Information (Detail) - USD ($)		12 Months Ended
	Nov. 20, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Business Acquisition [Line Items]
Sale of recognized pretax gain		$ 15,895,000
Proceeds from Sale of Productive Assets, Total		26,587,000	$ 0	$ 0
Lake Providence Louisiana [Member]
Business Acquisition [Line Items]
Assets held for sale property, plant and equipment net		3,500,000
Sale of recognized pretax gain		10,751,000
Proceeds from Sale of Productive Assets, Total		$ 15,087,000
Stepan Philippines Quaternaries, Inc.[Member]
Business Acquisition [Line Items]
Assets held for sale property, plant and equipment net	$ 3,753,000
Assets held for sale property, prepaid assets, mostly supplies and parts	1,707,000
Sale of recognized pretax gain	5,144,000
Proceeds from Sale of Productive Assets, Total	$ 11,500,000