Segment Information - Reconciliation of Reportable Segment Operating Income (Loss) to Corresponding Consolidated Amounts (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets			$ 17,200	$ 11,100
Restructuring Charges	$ 370	$ 47	429	48
Segment operating income (loss)	13,672	10,321	19,004	15,246
Operating Segments
Segment Reporting Information [Line Items]
Segment operating income (loss)	21,130	16,920	38,861	27,244
Segment Reconciling Items
Segment Reporting Information [Line Items]
Amortization of acquired intangible assets	6,614	4,629	12,382	9,217
Corporate, Non-Segment
Segment Reporting Information [Line Items]
Other unallocated corporate expenses	$ 474	$ 1,923	$ 7,046	$ 2,733

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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