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, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Restructuring and other charges	$ 860	$ 7,336	$ 1,835	$ 8,811
Total operating income (loss)	14,801	(6,339)	27,963	(14,659)
Operating Segments
Segment Reporting Information [Line Items]
Total operating income (loss)	21,293	4,441	38,776	2,779
Segment Reconciling Items
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets	3,294	3,091	6,358	5,302
Restructuring and other charges	860	7,336	1,835	8,811
Other unallocated corporate expenses	$ 2,338	$ 353	$ 2,620	$ 3,325