Significant Accounting Policies - Segment Reporting Revenue Percentage (Detail) - Sales Revenue, Segment [Member] - Segment Concentration Risk [Member]	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reinforcement Materials [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	52.00%	60.00%	55.00%	59.00%
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	35.00%	29.00%	33.00%	29.00%
Purification Solutions [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	11.00%	9.00%	10.00%	9.00%
Specialty Fluids [Member]
Segment Reporting Information [Line Items]
Revenue, by segment	2.00%	2.00%	2.00%	3.00%