Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net Sales		$ 499,335	$ 468,269
Cost of Sales		409,765	376,150
Gross Profit	[1]	89,570	92,119
Operating Expenses:
Selling	[1]	14,890	13,456
Administrative	[1]	19,439	17,892
Research, development and technical services	[1]	13,614	13,379
Deferred compensation expense		1,614	376
Total Operating expenses		49,557	45,103
Business restructuring expenses (Note 15)		(358)	(786)
Operating Income	[2]	39,655	46,230
Other Income (Expense):
Interest, net		(3,151)	(2,992)
Other, net (Note 14)	[1],[2]	1,160	1,092
Nonoperating Income (Expense), Total		(1,991)	(1,900)
Income Before Provision for Income Taxes		37,664	44,330
Provision for Income Taxes (Note 17)		6,948	12,418
Net Income		30,716	31,912
Net Loss Attributable to Noncontrolling Interests (Note 2)		7	1
Net Income Attributable to Stepan Company	[1]	$ 30,723	$ 31,913
Net Income Per Common Share Attributable to Stepan Company (Note 9):
Basic		$ 1.33	$ 1.39
Diluted		$ 1.31	$ 1.37
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 9):
Basic		23,082	22,901
Diluted		23,389	23,331
Dividends Declared Per Common Share		$ 0.23	$ 0.21

[1] The 2017 amounts for the noted line items have been immaterially changed from the amounts originally reported as a result of the Company’s first quarter 2018 adoption of Accounting Standards Update (ASU) No. 2017-7, Compensation –Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.

[2] The 2017 data has been immaterially changed from the amounts originally reported as a result of the Company’s first quarter 2018 adoption of ASU No. 2017-7, Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.