Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net Sales	$ 602,688	$ 464,480	$ 1,735,939	$ 1,375,016
Cost of Sales	510,792	367,423	1,423,382	1,100,195
Gross Profit	91,896	97,057	312,557	274,821
Operating Expenses:
Selling	14,786	13,266	44,280	39,719
Administrative	22,828	21,354	69,440	60,957
Research, development and technical services	15,501	14,303	45,638	41,661
Deferred compensation (income) expense	(1,504)	5,613	2,148	4,754
Total Operating expenses	51,611	54,536	161,506	147,091
Business restructuring expenses (Note 16)	(72)	(126)	(267)	(708)
Operating Income	40,213	42,395	150,784	127,022
Other Income (Expense):
Interest, net	(1,599)	(1,626)	(4,690)	(4,115)
Other, net (Note 15)	702	2,629	4,206	3,804
Nonoperating Income (Expense), Total	(897)	1,003	(484)	(311)
Income Before Provision for Income Taxes	39,316	43,398	150,300	126,711
Provision for Income Taxes	2,393	10,056	29,463	29,987
Net Income	36,923	33,342	120,837	96,724
Net Income Attributable to Noncontrolling Interest (Note 2)	(3)	(174)	(28)	(304)
Net Income Attributable to Stepan Company	$ 36,920	$ 33,168	$ 120,809	$ 96,420
Net Income Per Common Share Attributable to Stepan Company (Note 10):
Basic	$ 1.61	$ 1.45	$ 5.27	$ 4.20
Diluted	$ 1.59	$ 1.43	$ 5.19	$ 4.15
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 10):
Basic	22,898	22,907	22,941	22,951
Diluted	23,219	23,237	23,299	23,236