Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Name:	us-gaap_GoodwillImpairmentLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS, NET, Quantitative Analysis of Goodwill (Details) - USD ($)		12 Months Ended
	Jan. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Goodwill impairment		$ 0	$ 19,000,000	$ 0
Goodwill and intangible asset impairment	$ 0
Customer relationships
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Goodwill and intangible asset impairment	$ 0
Capital Markets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Goodwill impairment			$ 19,000,000
Silver Lane
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Time period over which goodwill is recognized			15 years