Reconciliations of Equity - Reconciliations of Total Equity (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reconciliations of total equity
Beginning Balance				$ 558,384	$ 536,944
Net income		$ 20,432	$ 24,934	75,959	63,161
Dividends				(12,732)	(12,067)
Common stock purchases	[1]			(2,643)	(2,273)
Stock option exercises				3,290	431
Defined benefit pension adjustments, net of tax		497	722	1,626	2,221
Translation adjustments		(2,213)	(19,793)	7,685	(38,988)
Derivative instrument activity, net of tax			(14)	(27)	(40)
Other	[2]			8,190	3,617
Ending Balance		639,732	553,006	639,732	553,006
Stepan Company Equity [Member]
Reconciliations of total equity
Beginning Balance				556,984	535,546
Net income				75,946	63,096
Dividends				(12,732)	(12,067)
Common stock purchases	[1]			(2,643)	(2,273)
Stock option exercises				3,290	431
Defined benefit pension adjustments, net of tax				1,626	2,221
Translation adjustments				7,722	(38,947)
Derivative instrument activity, net of tax				(27)	(40)
Other	[2]			8,190	3,617
Ending Balance		638,356	551,584	638,356	551,584
Noncontrolling Interests' Equity [Member]
Reconciliations of total equity
Beginning Balance	[3]			1,400	1,398
Net income	[3]			13	65
Translation adjustments	[3]			(37)	(41)
Ending Balance	[3]	$ 1,376	$ 1,422	$ 1,376	$ 1,422

[1] Includes the value of Company shares purchased in the open market and the value of Company common shares tendered by employees to settle minimum statutory withholding taxes related to the receipt of performance awards and deferred compensation distributions.

[2] Primarily comprised of activity related to stock-based compensation, deferred compensation and the related excess tax benefits.

[3] Reflects the noncontrolling interest in the Company’s China joint venture.