Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	[1],[2]	$ 25,880	$ 21,754	[3]	$ 81,068	$ 87,151	[3]
Other comprehensive income:
Foreign currency translation adjustments (Note 12)	[4]	(19,287)	(2,534)		(11,290)	(28,776)
Defined benefit pension adjustments, net of tax (Note 12)		473	788		1,558	2,293
Derivative instrument activity, net of tax (Note 12)		(2)	(2)		(6)	(7)
Total other comprehensive income		(18,816)	(1,748)		(9,738)	(26,490)
Comprehensive income	[1]	7,064	20,006		71,330	60,661
Comprehensive loss attributable to noncontrolling interests (Note 3)		41	31		62	55
Comprehensive income attributable to Stepan Company	[1]	$ 7,105	$ 20,037		$ 71,392	$ 60,716

[1] 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.

[2] 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 the last in, first out (LIFO) basis to the first in, first out (FIFO) basis.

[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.

[4] Includes foreign currency translation adjustments related to noncontrolling interest.