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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 12,684	$ 52,126	$ 28,826	$ 96,935
Weighted-average number of common shares outstanding		22,768	22,792	22,763	22,842
Basic earnings per share		$ 0.56	$ 2.29	$ 1.27	$ 4.24
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company		$ 12,684	$ 52,126	$ 28,826	$ 96,935
Weighted-average number of common shares outstanding		22,768	22,792	22,763	22,842
Add weighted-average net shares related to unvested stock awards (under treasury stock method)		3		2
Weighted-average shares applicable to diluted earnings		22,945	23,055	22,970	23,115
Diluted earnings per share		$ 0.55	$ 2.26	$ 1.25	$ 4.19
Employee Stock Option
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury stock method)	[1]	71	102	85	106
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]	73	106	90	113
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury stock method)		30	55	30	54

[1] 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. 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. 337,056 and 350,703 options/SARs to acquire shares of Company common stock were excluded from the computation of dilutive earnings per share for the three and six months ended June 30, 2022, respectively.