Segment and Geographic Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets	$ 17,100	$ 15,000	$ 12,900
Restructuring Charges	3,226	12,039	4,713
Total operating income (loss)	64,113	4,238	16,890
Operating Segments
Segment Reporting Information [Line Items]
Total operating income (loss)	91,411	31,476	30,115
Segment Reconciling Items
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets	13,929	10,799	7,656
Restructuring Charges	3,226	12,039	4,713
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate expenses	$ 10,143	$ 4,400	$ 856