Summary of Significant Accounting Policies - Acquisition-Related Costs (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Business Combination, Integration Related Costs	$ 8,131	$ 16,059	$ 15,192
Professional service fees	2,321	3,450	12,622
Acquisition-related adjustments	(1,543)	(3,416)	(106)
Acquisition-related costs, net	$ 8,909	$ 16,093	$ 27,708

Acquisition-related costs include those costs related to business and other acquisitions, including potential acquisitions. These costs consist of (i) transition and integration costs, including retention payments, transitional employee costs and earn-out payments treated as compensation expense, as well as the costs of integration-related services provided by third-parties; (ii) professional service fees, including third party costs related to the acquisition, and legal and other professional service fees associated with disputes and regulatory matters related to acquired entities; and (iii) adjustments to acquisition-related items that are required to be marked to fair value each reporting period, such as contingent consideration, and other items related to acquisitions for which the measurement period has ended.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration