Financial Information about Segment Operations (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended			24 Months Ended
	Jun. 30, 2011	Sep. 30, 2009	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2006
Segment Reporting Information [Line Items]
Revenues			$ 215,085	$ 185,627	$ 160,714
Operating Expenses			(45,865)	(39,066)	(35,895)
Environmental Remediation Charges	(6,000)	(13,700)		(700)	(6,000)	(26,000)
Operating Income (Loss)			41,089	28,098	7,885
Depreciation and amortization			13,453	13,700	14,058
Capital Expenditures			13,916	8,788	11,931
Total Assets			277,307	246,464	229,806
Total Operating Segments
Segment Reporting Information [Line Items]
Operating Income (Loss)			58,190	43,124	28,009
Total Operating Segments | Fine Chemicals
Segment Reporting Information [Line Items]
Revenues			124,898	111,536	89,497
Operating Income (Loss)			11,295	8,678	(6,283)
Depreciation and amortization			12,013	11,914	12,473
Capital Expenditures			11,138	7,383	11,153
Total Assets			154,707	143,551	144,003
Total Operating Segments | Specialty Chemicals
Segment Reporting Information [Line Items]
Revenues			82,636	68,513	66,905
Operating Income (Loss)			47,961	34,919	35,600
Depreciation and amortization			1,144	1,401	1,136
Capital Expenditures			2,661	1,353	756
Total Assets			27,427	21,029	19,785
Total Operating Segments | Other Businesses
Segment Reporting Information [Line Items]
Revenues			7,551	5,578	4,312
Operating Income (Loss)			(1,066)	(473)	(1,308)
Depreciation and amortization			21	18	17
Capital Expenditures			6	18	8
Total Assets			5,319	7,302	5,064
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Operating Expenses			(17,101)	(14,326)	(14,124)
Depreciation and amortization			275	367	432
Capital Expenditures			111	34	14
Total Assets			$ 89,854	$ 74,582	$ 60,954