Geographic Data - Schedule Of Geographic Information (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020
Segment Reporting Information [Line Items]
Long-lived assets	$ 663.3	$ 718.1	$ 737.4
U.S. [Member]
Segment Reporting Information [Line Items]
Long-lived assets	652.9	708.2	727.0
Canada [Member]
Segment Reporting Information [Line Items]
Long-lived assets	$ 10.4	$ 9.9	$ 10.4

Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Name:	us-gaap_NoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant