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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 27,865	$ 16,914	$ 55,519	$ 38,184
Weighted-average number of common shares outstanding		22,760	22,742	22,746	22,731
Basic earnings per share		$ 1.22	$ 0.74	$ 2.44	$ 1.68
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company		$ 27,865	$ 16,914	$ 55,519	$ 38,184
Weighted-average number of common shares outstanding		22,760	22,742	22,746	22,731
Add weighted-average net shares issuable from assumed exercise of options (under treasury stock method)	[1]	125	127	119	116
Add weighted-average net shares related to unvested stock awards (under treasury stock method)		5	2	5	3
Weighted-average shares applicable to diluted earnings		22,958	22,871	22,920	22,850
Diluted earnings per share		$ 1.21	$ 0.74	$ 2.42	$ 1.67
Stock Appreciation Rights (SARs) [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares issuable from assumed exercise of options (under treasury stock method)		38	0	23	0
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares issuable from assumed exercise of options (under treasury stock method)		30	0	27	0

[1] Options to purchase 85,243 and 87,430 shares of Company common stock were excluded from the computations of diluted earnings per share for the three and six months ended June 30, 2016, respectively. Options to purchase 91,678 and 158,888 shares of Company common stock were excluded from the computations of diluted earnings per share for the three and six months ended June 30, 2015, respectively. The options’ exercise prices were greater than the average market price for the common stock and their effect would have been antidilutive.