Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net Sales		$ 487,814	$ 445,030	$ 1,451,184	$ 1,345,530
Cost of Sales		412,212	361,635	1,193,518	1,075,705
Gross Profit		75,602	83,395	257,666	269,825
Operating Expenses:
Selling		13,740	13,990	40,484	42,252
Administrative		18,557	18,958	54,376	55,350
Research, development and technical services		12,699	14,268	40,416	42,306
Deferred compensation expense		(129)	7,441	5,263	12,595
Total Operating expenses		44,867	54,657	140,539	152,503
Business restructuring expenses (Note 14)		426		1,798	1,061
Operating Income		30,309	28,738	115,329	116,261
Other Income (Expense):
Interest, net		(2,763)	(2,824)	(8,618)	(9,855)
Other, net (Note 13)		1,766	1,229	3,994	401
Nonoperating Income (Expense), Total		(997)	(1,595)	(4,624)	(9,454)
Income Before Provision for Income Taxes		29,312	27,143	110,705	106,807
Provision for Income Taxes	[1]	7,459	5,776	29,044	29,020
Net Income	[1]	21,853	21,367	81,661	77,787
Net (Income) Loss Attributable to Noncontrolling Interests (Note 2)		46	(5)	33	(13)
Net Income Attributable to Stepan Company	[1]	$ 21,899	$ 21,362	$ 81,694	$ 77,774
Net Income Per Common Share Attributable to Stepan Company (Note 9):
Basic	[1]	$ 0.95	$ 0.94	$ 3.56	$ 3.42
Diluted	[1]	$ 0.94	$ 0.92	$ 3.50	$ 3.38
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 9):
Basic		22,971	22,819	22,941	22,771
Diluted	[1]	23,374	23,148	23,361	23,017
Dividends Declared Per Common Share		$ 0.21	$ 0.19	$ 0.62	$ 0.57

[1] The 2016 amounts for the noted items have been immaterially changed from the amounts originally reported as a result of the Company’s fourth quarter 2016 adoption of Accounting Standards Update (ASU) No. 2016-9, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.