Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 40,204	$ 147,153	$ 137,804
Weighted-average number of shares outstanding		22,777	22,781	22,922
Basic earnings per share		$ 1.77	$ 6.46	$ 6.01
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company		$ 40,204	$ 147,153	$ 137,804
Weighted-average number of shares outstanding		22,777	22,781	22,922
Add weighted-average net shares related to unvested stock awards (under treasury share method)		3	1	1
Weighted-average shares applicable to diluted earnings		22,946	23,064	23,287
Diluted earnings per share		$ 1.75	$ 6.38	$ 5.92
Stock Option [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury share method)	[1]	66	104	138
Stock Appreciation Rights (SARs)
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury share method)		67	111	166
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury share method)		33	67	60

[1] Options/SARs to purchase 672,485, 343,715 and 103,182 shares of the Company’s common stock were excluded from the computations of diluted earnings per share for the years ended December 31, 2023, 2022 and 2021, respectively. The options’/SARs’ exercise prices were greater than the average market price for the Company’s common stock and inclusion of the instruments would have had an antidilutive effect on the computations of earnings per share.