Condensed Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net Sales		$ 489,170	$ 499,335
Cost of Sales	[1]	404,561	408,137
Gross Profit	[1]	84,609	91,198
Operating Expenses:
Selling		13,969	14,890
Administrative		19,306	19,439
Research, development and technical services		13,390	13,614
Deferred compensation expense		7,473	1,614
Total Operating expenses		54,138	49,557
Business restructuring expenses (Note 17)		(733)	(358)
Operating Income	[1],[2]	29,738	41,283
Other Income (Expense):
Interest, net		(1,853)	(3,151)
Other, net (Note 16)		3,145	1,160
Nonoperating Income (Expense), Total		1,292	(1,991)
Income Before Provision for Income Taxes	[1],[2]	31,030	39,292
Provision for Income Taxes	[1]	6,052	7,347
Net Income	[1],[2]	24,978	31,945	[3]
Net Loss Attributable to Noncontrolling Interests (Note 3)		6	7
Net Income Attributable to Stepan Company	[1],[2]	$ 24,984	$ 31,952
Net Income Per Common Share Attributable to Stepan Company (Note 11):
Basic	[1],[2]	$ 1.08	$ 1.38
Diluted	[1],[2]	$ 1.07	$ 1.37
Shares Used to Compute Net Income Per Common Share Attributable to Stepan Company (Note 11):
Basic		23,099	23,082
Diluted		23,332	23,389

[1] The 2018 amounts for the noted line items have been 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 the last in, first out (LIFO) basis to the first in, first out (FIFO) basis.

[2] The 2018 amounts for the noted line items have been 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 retained earnings and net income amounts for the noted line items have been 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.