Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Computation of Basic Earnings per Share
Net income attributable to Stepan Company	$ 21,425	$ 20,867	$ 43,727	$ 39,628
Deduct dividends on preferred stock	177	179	355	358
Income applicable to common stock	21,248	20,688	43,372	39,270
Weighted-average number of shares outstanding	10,550	10,345	10,537	10,335
Basic earnings per share	$ 2.01	$ 2.00	$ 4.12	$ 3.80
Computation of Diluted Earnings per Share
Net income attributable to Stepan Company	$ 21,425	$ 20,867	$ 43,727	$ 39,628
Weighted-average number of shares outstanding	10,550	10,345	10,537	10,335
Add weighted-average net shares issuable from assumed exercise of options (under treasury stock method) (1)	212	237	213	244
Add weighted-average net shares related to unvested stock awards (under treasury stock method)	3	2	3	2
Add weighted-average shares issuable from assumed conversion of convertible preferred stock	592	594	592	594
Weighted-average shares applicable to diluted earnings	11,357	11,178	11,345	11,175
Diluted	$ 1.89	$ 1.87	$ 3.85	$ 3.55