Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net Income	[1]	$ 103,101	$ 111,105	[2],[3]	$ 100,743	[3]
Other Comprehensive Income (Loss):
Foreign currency translation adjustments (Note 20)		4,425	(37,966)		26,293
Defined benefit pension plans:
Net actuarial gain (loss) arising in period (net of taxes of $1,263, $2,300 and $771 for 2019, 2018 and 2017, respectively)		4,112	(7,080)		(582)
Amortization of prior service cost included in pension expense (net of taxes of $3, $3 and $4 for 2019, 2018 and 2017, respectively)		9	10		10
Amortization of actuarial loss included in pension expense (net of taxes of $657, $979 and $1,240 for 2019, 2018 and 2017, respectively)		2,082	3,080		2,269
Net defined benefit pension plan activity (Note 20)		6,203	(3,990)		1,697
Cash flow hedges:
Reclassifications to income in period		(9)	(10)		(9)
Net cash flow hedge activity (Note 20)		(9)	(10)		(9)
Other Comprehensive Income (Loss)		10,619	(41,966)		27,981
Comprehensive Income	[1]	113,720	69,139		128,724
Comprehensive (Income) Loss Attributable to Noncontrolling Interests		47	58		(48)
Comprehensive Income Attributable to Stepan Company	[1]	$ 113,767	$ 69,197		$ 128,676

[1] 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.

[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 LIFO to FIFO

[3] 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.