Reconciliation of Reportable Segment Operating Income to Corresponding Consolidated Amounts (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other unallocated corporate expenses	$ 518	$ 231
Amortization of acquired intangible assets	1,217	450
Restructuring charges	203	214
Operating income (loss)	1,463	23,729
Operating Segments, Total
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	$ 3,401	$ 24,624