Acquisitions - Additional Information (Detail)					3 Months Ended												12 Months Ended
		Oct. 03, 2016 USD ($) Customer T	Oct. 03, 2016 BRL	Jun. 15, 2015 USD ($) T	Dec. 31, 2016 USD ($)		Sep. 30, 2016 USD ($)		Jun. 30, 2016 USD ($)		Mar. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)		Oct. 03, 2016 BRL Customer T
Business And Asset Acquisition [Line Items]
Paid from cash on hand																	$ 23,510,000		$ 5,133,000
Net sales					$ 420,636,000		$ 445,030,000		$ 454,603,000		$ 445,897,000		$ 419,291,000	$ 444,011,000	$ 452,414,000	$ 460,451,000	1,766,166,000	[1]	1,776,167,000	[1]	$ 1,927,213,000	[1]
Net income					8,417,000	[2]	$ 21,362,000	[2]	$ 28,496,000	[2]	$ 27,916,000	[2]	12,872,000	$ 24,912,000	$ 16,914,000	$ 21,270,000	86,191,000	[2]	75,968,000		57,101,000
Goodwill					25,308,000								11,265,000				25,308,000		11,265,000		11,502,000
Asset acquisition purchase price																	$ 103,076,000		119,349,000		101,819,000
Sun Products Corporation's (SUN's) Pasadena, Texas [Member]
Business And Asset Acquisition [Line Items]
Asset acquisition purchase price																			13,000,000
Acquisition of land																			3,377,000
Acquisition of manufacturing assets																			9,623,000
Non-compete Agreements [Member]
Business And Asset Acquisition [Line Items]
Amortization periods for the identifiable intangible assets at the time of acquisition																	5 years
Minimum [Member] | Customer Relationships [Member]
Business And Asset Acquisition [Line Items]
Amortization periods for the identifiable intangible assets at the time of acquisition																	10 years
Maximum [Member] | Customer Relationships [Member]
Business And Asset Acquisition [Line Items]
Amortization periods for the identifiable intangible assets at the time of acquisition																	13 years
Brazil [Member]
Business And Asset Acquisition [Line Items]
Net sales	[1]																$ 74,961,000		63,439,000		65,165,000
Surfactants [Member]
Business And Asset Acquisition [Line Items]
Goodwill					$ 19,491,000								$ 5,402,000				$ 19,491,000		5,402,000		$ 5,558,000
Tebras And PBC [Member]
Business And Asset Acquisition [Line Items]
Acquisition of intangible assets		$ 7,354,000
Acquisition of property, plant and equipment		5,716,000
Acquisition of liabilities		3,487,000
Goodwill		14,327,000
Tebras And PBC [Member] | Customer Relationships [Member]
Business And Asset Acquisition [Line Items]
Acquisition of intangible assets		4,331,000
Amortization periods for the identifiable intangible assets at the time of acquisition																	13 years
Tebras And PBC [Member] | Supply Contract [Member]
Business And Asset Acquisition [Line Items]
Acquisition of intangible assets		2,555,000
Amortization periods for the identifiable intangible assets at the time of acquisition																	4 years
Tebras And PBC [Member] | Non-compete Agreements [Member]
Business And Asset Acquisition [Line Items]
Acquisition of intangible assets		468,000
Amortization periods for the identifiable intangible assets at the time of acquisition																	5 years
Tebras And PBC [Member] | Brazil [Member]
Business And Asset Acquisition [Line Items]
Net sales																			28,000,000
Tebras And PBC [Member] | Brazil [Member] | Maximum [Member]
Business And Asset Acquisition [Line Items]
Net income																			$ 2,000,000
Tebras And PBC [Member] | Surfactants [Member]
Business And Asset Acquisition [Line Items]
Acquisition-related expenses		$ 250,000
Tebras And PBC [Member] | Surfactants [Member] | Brazil [Member]
Business And Asset Acquisition [Line Items]
Capacity of production facility | T		25,000																					25,000
Acquisitions purchase price, including adjustments for working capital		$ 29,075,000																					BRL 93,309,000
Paid from cash on hand		21,812,000	BRL 70,000,000
Deposited in escrow		2,804,000																					9,000,000
Unpaid working capital adjustments		$ 4,459,000																					BRL 14,309,000
Tebras And PBC [Member] | Surfactants [Member] | Brazil [Member] | Minimum [Member]
Business And Asset Acquisition [Line Items]
Number of customers | Customer		1,200																					1,200
Procter and Gamble Company [Member] | Brazil [Member]
Business And Asset Acquisition [Line Items]
Capacity of production facility | T				30,000
Paid from cash on hand				$ 5,133,000
Acquisition of intangible assets				0
Acquisition of property, plant and equipment				6,007,000
Acquisition of liabilities				874,000
Goodwill				$ 0

[1] Net sales are attributed to countries based on the location of the Company facility making the sales.

[2] The amounts for net income, net income attributable to Stepan Company and net income attributable to Stepan Company per diluted share for the first, second and third quarters of 2016 have been changed from the amounts originally reported as a result of the Company’s early adoption of ASU No. 2016-9, Compensation – Stock Compensation (Topic 718): Improvement to Employee Share-Based Payment Accounting. See Note 1 for additional information regarding ASU No. 2016-9. Below are the originally reported amounts for the items that changed: 2016 (In thousands, except per share data) First Second Third Net Income $27,657 $27,870 $20,432 Net Income Attributable to Stepan Company 27,654 27,865 20,427 Per Diluted Share 1.21 1.21 0.89