Segment and Geographic Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets	$ 24,200	$ 17,100	$ 14,800
Restructuring Charges	714	3,144	10,210
Total operating income (loss)	31,409	14,319	(17,054)
Operating Segments
Segment Reporting Information [Line Items]
Total operating income (loss)	59,533	41,520	10,183
Segment Reconciling Items
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets	19,339	13,228	10,799
Restructuring Charges	714	3,144	10,210
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate expenses	$ 8,071	$ 10,829	$ 6,228