XML 20 R2.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Audit Information - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Jun. 30, 2024
Audit Information [Abstract] |  |
Auditor Name | KPMG LLP |
Auditor Location | St. Louis, MO |
Auditor Firm ID | 185 |
Document Financial Statement Error Correction [Flag] | false |
Entity Public Float |  | $ 529.5

X
- Definition Audit Information [Abstract] + References No definition available. + Details
Name: | cass_AuditInformationAbstract
Namespace Prefix: | cass_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition PCAOB issued Audit Firm Identifier + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_AuditorFirmId
Namespace Prefix: | dei_
Data Type: | dei:nonemptySequenceNumberItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_AuditorLocation
Namespace Prefix: | dei_
Data Type: | dei:internationalNameItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_AuditorName
Namespace Prefix: | dei_
Data Type: | dei:internationalNameItemType
Balance Type: | na
Period Type: | duration

X
- Definition Indicates whether any of the financial statement period in the filing include a restatement due to error correction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection w Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 10-K -Number 249 -Section 310 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 20-F -Number 249 -Section 220 -Subsection f Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form 40-F -Number 249 -Section 240 -Subsection f + Details
Name: | dei_DocumentFinStmtErrorCorrectionFlag
Namespace Prefix: | dei_
Data Type: | xbrli:booleanItemType
Balance Type: | na
Period Type: | duration

X
- Definition The aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked price of such common equity, as of the last business day of the registrant's most recently completed second fiscal quarter. + References No definition available. + Details
Name: | dei_EntityPublicFloat
Namespace Prefix: | dei_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant