Reconciliation of Reportable Segment Operating Income to Corresponding Consolidated Amounts (Detail) (USD $)	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other unallocated corporate expenses	$ (2,934,000)	$ 303,000	$ (2,416,000)	$ 534,000
Amortization of acquired intangible assets	1,138,000	449,000	2,355,000	899,000
Restructuring charges	42,000	246,000	245,000	460,000
In-process research and development	3,026,000		3,026,000
Operating income (loss)	8,415,000	26,741,000	9,878,000	50,470,000
Operating Segments, Total
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	$ 9,687,000	$ 27,739,000	$ 13,088,000	$ 52,363,000