Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 112,750	$ 91,547	$ 86,198
Other Comprehensive Income (Loss):
Foreign currency translation adjustments (Note 19)	(37,966)	26,293	(8,533)
Defined benefit pension plans:
Net actuarial gain (loss) arising in period (net of taxes of $2,300, $771 and $3,391 for 2018, 2017 and 2016, respectively)	(7,080)	(582)	3,818
Amortization of prior service cost included in pension expense (net of taxes of $3, $4 and $4 for 2018, 2017 and 2016, respectively)	10	10	10
Amortization of actuarial loss included in pension expense (net of taxes of $979, $1,240 and $1,301 for 2018, 2017 and 2016, respectively)	3,080	2,269	2,207
Net defined benefit pension plan activity (Note 19)	(3,990)	1,697	6,035
Cash flow hedges:
Losses arising in period (net of taxes of $0, $0 and $9 in 2018, 2017 and 2016, respectively)			(19)
Reclassifications to income in period (net of taxes of $0, $0 and $28 in 2018, 2017 and 2016, respectively)	(10)	(9)	45
Net cash flow hedge activity (Note 19)	(10)	(9)	26
Other Comprehensive Income (Loss)	(41,966)	27,981	(2,472)
Comprehensive Income	70,784	119,528	83,726
Comprehensive (Income) Loss Attributable to Noncontrolling Interests	58	(48)	88
Comprehensive Income Attributable to Stepan Company	$ 70,842	$ 119,480	$ 83,814