Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended												12 Months Ended
		Dec. 31, 2016	[1]	Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016	[1]	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Computation of Basic Earnings per Share
Net income attributable to Stepan Company		$ 8,417		$ 21,362		$ 28,496		$ 27,916		$ 12,872	$ 24,912	$ 16,914	$ 21,270	$ 86,191	[1]	$ 75,968	$ 57,101
Weighted-average number of shares outstanding														22,793		22,730	22,758
Basic earnings per share														$ 3.78		$ 3.34	$ 2.51
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company														$ 86,191		$ 75,968	$ 57,101
Weighted-average number of shares outstanding														22,793		22,730	22,758
Add weighted-average net shares issuable from assumed exercise of options (under treasury share method)	[2]													159		118	148
Add weighted-average net shares related to unvested stock awards (under treasury share method)														6		3	11
Weighted-average shares applicable to diluted earnings														23,094		22,858	22,917
Diluted earnings per share		$ 0.36		$ 0.92		$ 1.24		$ 1.22		$ 0.56	$ 1.09	$ 0.74	$ 0.93	$ 3.73	[1]	$ 3.32	$ 2.49
Performance Stock Award [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares issuable from assumed exercise of options (under treasury share method)														68		6
Stock Appreciation Rights (SARs) [Member]
Computation of Diluted Earnings per Share
Add weighted-average net shares issuable from assumed exercise of options (under treasury share method)														68		1

[1] The amounts for net income, net income attributable to Stepan Company and net income attributable to Stepan Company per diluted share for the first, second and third quarters of 2016 have been changed from the amounts originally reported as a result of the Company’s early adoption of ASU No. 2016-9, Compensation – Stock Compensation (Topic 718): Improvement to Employee Share-Based Payment Accounting. See Note 1 for additional information regarding ASU No. 2016-9. Below are the originally reported amounts for the items that changed: 2016 (In thousands, except per share data) First Second Third Net Income $27,657 $27,870 $20,432 Net Income Attributable to Stepan Company 27,654 27,865 20,427 Per Diluted Share 1.21 1.21 0.89

[2] Options to purchase 43,715, 124,531 and 99,044 shares of common stock were not included in the computations of diluted earnings per share for the years ended December 31, 2016, 2015 and 2014, respectively. The options’ exercise prices were greater than the average market price for the common stock and the effect of the options on earnings per share would have been antidilutive.