Sale of Assets - Additional Information (Detail) - USD ($)	Jun. 30, 2025	May 27, 2025	Dec. 31, 2024
Business Acquisition [Line Items]
Assets	$ 2,416,130,000		$ 2,304,648,000
Assets held for sale	8,663,000
Liabilities held for sale	4,813,000
Property, plant and equipment, net	1,212,928,000		1,198,454,000
Operating leases	63,274,000		71,477,000
Current operating lease liabilities	14,487,000
Non-current operating lease liabilities	50,100,000		57,392,000
Operating Segments [Member]
Business Acquisition [Line Items]
Assets	2,287,842,000		2,172,779,000
Operating Segments [Member] | Surfactants [Member]
Business Acquisition [Line Items]
Assets	$ 1,654,136,000		$ 1,578,689,000
Operating Segments [Member] | Surfactants [Member] | Stepan Philippines Quaternaries, Inc.[Member]
Business Acquisition [Line Items]
Assets held for sale		$ 8,663,000
Liabilities held for sale		4,813,000
Liabilities held for sale operating lease liabilities		4,813,000
Assets held for sale property, plant and equipment net		3,820,000
Assets held for sale operating lease right-of use assets		$ 4,843,000