Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Net Sales	$ 595,511	$ 460,549	$ 1,133,251	$ 910,536
Cost of Sales	483,830	362,054	912,590	732,772
Gross Profit	111,681	98,495	220,661	177,764
Operating Expenses:
Selling	14,990	12,921	29,494	26,453
Administrative	23,974	20,731	46,612	39,603
Research, development and technical services	14,988	13,531	30,137	27,358
Deferred compensation (income) expense	958	6,464	3,652	(859)
Total Operating expenses	54,910	53,647	109,895	92,555
Business restructuring expenses (Note 16)	(114)	(225)	(195)	(582)
Operating Income	56,657	44,623	110,571	84,627
Other Income (Expense):
Interest, net	(1,567)	(1,259)	(3,091)	(2,489)
Other, net (Note 15)	2,758	4,437	3,504	1,175
Nonoperating Income (Expense), Total	1,191	3,178	413	(1,314)
Income Before Provision for Income Taxes	57,848	47,801	110,984	83,313
Provision for Income Taxes	14,545	11,958	27,070	19,931
Net Income	43,303	35,843	83,914	63,382
Net Income Attributable to Noncontrolling Interest (Note 2)	(25)	(136)	(25)	(130)
Net Income Attributable to Stepan Company	$ 43,278	$ 35,707	$ 83,889	$ 63,252
Net Income Per Common Share Attributable to Stepan Company (Note 10):
Basic	$ 1.89	$ 1.56	$ 3.65	$ 2.75
Diluted	$ 1.85	$ 1.54	$ 3.59	$ 2.72
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 10):
Basic	22,952	22,923	22,963	22,973
Diluted	23,345	23,184	23,338	23,235