Nonconsolidated Variable Interest Entities (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 811.3	$ 649.6
Investments [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss	639.2	439.2
Receivables [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss	172.1	168.0
Loans Receivables [Member]
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 0.0	$ 42.4

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121559654&loc=d3e5747-111685

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=121559654&loc=d3e5728-111685

Name:	us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant