Segment Reporting - Operating Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Net sales	$ 419,291	$ 444,011	$ 452,414	$ 460,451	$ 454,231	$ 491,429	$ 504,111	$ 477,442	$ 1,776,167	[1]	$ 1,927,213	[1]	$ 1,880,786	[1]
Operating income	20,223	$ 38,794	$ 28,595	$ 35,178	9,004	$ 22,253	$ 36,914	$ 22,523	122,790		90,694		109,153
Assets	1,239,661				1,162,014				1,239,661		1,162,014		1,167,202
Capital expenditures									119,349		101,819		92,865
Depreciation and amortization expenses									66,985		63,804		56,400
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									1,776,167		1,927,213		1,880,786
Operating income									189,419		131,955		165,639
Assets	1,124,918				1,129,905				1,124,918		1,129,905		1,070,949
Capital expenditures									116,867		98,823		91,440
Depreciation and amortization expenses									65,322		62,708		55,382
Surfactants [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									1,205,849		1,296,638		1,317,164
Operating income									104,080		60,778		100,201
Assets	758,524				741,677				758,524		741,677		710,521
Capital expenditures									79,171		70,796		66,266
Depreciation and amortization expenses									42,122		41,483		36,400
Polymers [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									491,488		550,966		483,361
Operating income									80,942		60,690		54,536
Assets	293,790				320,640				293,790		320,640		292,015
Capital expenditures									31,309		22,409		18,804
Depreciation and amortization expenses									19,541		18,433		16,351
Specialty Products [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									78,830		79,609		80,261
Operating income									4,397		10,487		10,902
Assets	$ 72,604				$ 67,588				72,604		67,588		68,413
Capital expenditures									6,387		5,618		6,370
Depreciation and amortization expenses									$ 3,659		$ 2,792		$ 2,631

[1] Net sales are attributed to countries based on selling location.