Earnings Per Share - Computations of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 9,521	$ 12,684	$ 23,414	$ 28,826
Weighted-average number of common shares outstanding		22,827	22,768	22,825	22,763
Basic earnings per share		$ 0.42	$ 0.56	$ 1.03	$ 1.27
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company		$ 9,521	$ 12,684	$ 23,414	$ 28,826
Weighted-average number of common shares outstanding		22,827	22,768	22,825	22,763
Add weighted-average net shares related to unvested stock awards (under treasury stock method)		8	3	6	2
Weighted-average shares applicable to diluted earnings		22,936	22,945	22,942	22,970
Diluted earnings per share		$ 0.42	$ 0.55	$ 1.02	$ 1.25
Stock Option [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury stock method)	[1]	34	71	41	85
Stock Appreciation Rights (SARs) [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury stock method)	[1]	45	73	49	90
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury stock method)		22	30	21	30

[1] 899,151 and 849,588 options/SARs to acquire shares of the Company's common stock were excluded from the computation of dilutive earnings per share for the three and six months ended June 30, 2024, 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 the earnings per share. 644,962 and 524,337 options/SARs to acquire shares of the Company's common stock were excluded from the computation of dilutive earnings per share for the three and six months ended June 30, 2023, respectively.