Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Income Statement [Abstract]
Net Sales (Note 1)	[1]	$ 1,858,745	$ 1,993,857		$ 1,925,007
Cost of Sales	[2]	1,519,031	1,654,508		1,578,840
Gross Profit	[2]	339,714	339,349	[3]	346,167
Operating Expenses:
Selling (Note 1)		56,956	56,319		54,090
Administrative (Note 1)		82,577	79,243		75,615
Research, development and technical services (Note 1)		55,037	54,263		53,696
Deferred compensation expense (income)		15,140	(2,329)		4,857
Total Operating expenses		209,710	187,496		188,258
Business restructuring (Note 23)	[4]	(2,744)	(2,588)		(3,069)
Operating Income	[2]	127,260	149,265	[3]	154,840
Other Income (Expense):
Interest, net (Note 7)		(5,932)	(10,771)		(11,444)
Other, net (Note 9)		4,571	(725)		3,486
Nonoperating Income (Expense), Total		(1,361)	(11,496)		(7,958)
Income Before Provision for Income Taxes	[2],[5]	125,899	137,769	[3]	146,882
Provision for Income Taxes (Note 10)	[2]	22,798	26,664		46,139
Net Income	[2]	103,101	111,105	[3],[6]	100,743	[6]
Net Loss Attributable to Noncontrolling Interests (Note 1)		28	12		31
Net Income Attributable to Stepan Company	[2]	$ 103,129	$ 111,117	[3]	$ 100,774
Net Income Per Common Share Attributable to Stepan Company (Note 19):
Basic	[2]	$ 4.47	$ 4.83		$ 4.39
Diluted	[2]	$ 4.42	$ 4.76	[3]	$ 4.31
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 19):
Basic		23,054	23,022		22,946
Diluted		23,316	23,325		23,377

[1] Net sales are attributed to countries based on the location of the Company facility making the sales.

[2] The 2018 and 2017 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.

[3] The 2018 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO

[4] See Note 23 regarding business restructuring costs.

[5] The 2018 and 2017 amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO

[6] The retained earnings and net income amounts for the noted line items have been retrospectively changed from the amounts originally reported as a result of the Company’s first quarter 2019 change in method of accounting for U.S. inventory valuation from LIFO to FIFO.