Segment Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Amortization of acquired intangible assets	$ 3,091	$ 1,914	$ 5,302	$ 3,826
Restructuring and other charges	7,336	685	8,811	3,353
Other unallocated corporate expenses	353	60	3,325	459
Operating income (loss)	(6,339)	3,053	(14,659)	(3,427)
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income (loss)	$ 4,441	$ 5,712	$ 2,779	$ 4,211