Customer Accounts - Narrative (Details) - USD ($)	Sep. 30, 2023	Sep. 30, 2022
Banking and Thrift, Interest [Abstract]
Uninsured deposits	$ 4,124,355,000	$ 4,856,148,927

Amount of uninsured deposit liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1406
-Paragraph (e)
-Publisher SEC

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