Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Net Sales	$ 420,636		$ 445,030		$ 454,603		$ 445,897		$ 419,291	$ 444,011	$ 452,414	$ 460,451	$ 1,766,166	[1]	$ 1,776,167	[1]	$ 1,927,213	[1]
Gross Profit	68,720		83,395		92,931		93,499		74,689	77,598	79,512	76,442	338,545		308,241		249,563
Operating income	9,932		28,738		42,916		44,607		20,223	38,794	28,595	35,178	126,193		122,790		90,694
Interest, net	(3,350)		(2,824)		(3,417)		(3,614)		(3,773)	(3,837)	(2,869)	(4,054)	(13,205)		(14,533)		(11,441)
Income Before Income Taxes	7,009		27,143		39,196		40,468		15,061	33,113	24,146	30,536	113,816		102,856		75,535
Net Income	8,411	[2]	21,367	[2]	28,501	[2]	27,919	[2]	12,876	24,934	16,941	21,286	86,198	[2]	76,037		57,081
Net income attributable to Stepan Company	$ 8,417	[2]	$ 21,362	[2]	$ 28,496	[2]	$ 27,916	[2]	$ 12,872	$ 24,912	$ 16,914	$ 21,270	$ 86,191	[2]	$ 75,968		$ 57,101
Diluted earnings per share	$ 0.36	[2]	$ 0.92	[2]	$ 1.24	[2]	$ 1.22	[2]	$ 0.56	$ 1.09	$ 0.74	$ 0.93	$ 3.73	[2]	$ 3.32		$ 2.49

[1] Net sales are attributed to countries based on the location of the Company facility making the sales.

[2] 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