Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net Sales	$ 537,740	$ 449,987
Cost of Sales	428,760	370,718
Gross Profit	108,980	79,269
Operating Expenses:
Selling	14,504	13,532
Administrative	22,638	18,872
Research, development and technical services	15,149	13,827
Deferred compensation (income) expense	2,694	(7,323)
Total Operating expenses	54,985	38,908
Business restructuring expenses (Note 16)	(81)	(357)
Operating Income	53,914	40,004
Other Income (Expense):
Interest, net	(1,524)	(1,230)
Other, net (Note 15)	746	(3,262)
Nonoperating Income (Expense), Total	(778)	(4,492)
Income Before Provision for Income Taxes	53,136	35,512
Provision for Income Taxes	12,525	7,973
Net Income	40,611	27,539
Net Loss Attributable to Noncontrolling Interests (Note 2)		6
Net Income Attributable to Stepan Company	$ 40,611	$ 27,545
Net Income Per Common Share Attributable to Stepan Company (Note 10):
Basic	$ 1.77	$ 1.20
Diluted	$ 1.74	$ 1.18
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 10):
Basic	22,974	23,023
Diluted	23,330	23,285