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, 2022	Dec. 31, 2021	Dec. 31, 2020
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 147,153	$ 137,804	$ 126,770
Weighted-average number of shares outstanding		22,781	22,922	22,949
Basic earnings per share		$ 6.46	$ 6.01	$ 5.52
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company		$ 147,153	$ 137,804	$ 126,770
Weighted-average number of shares outstanding		22,781	22,922	22,949
Add weighted-average net shares related to unvested stock awards (under treasury share method)		1	1	1
Weighted-average shares applicable to diluted earnings		23,064	23,287	23,256
Diluted earnings per share		$ 6.38	$ 5.92	$ 5.45
Stock Option [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury share method)	[1]	104	138	112
Stock Appreciation Rights (SARs) [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury share method)		111	166	145
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares from assumed exercise of options (under treasury share method)		67	60	49

[1] Options/SARs to purchase 343,715, 103,182 and 127,434 shares of the Company’s common stock were excluded from the computations of diluted earnings per share for the years ended December 31, 2022, 2021 and 2020, 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.