Basis of Presentation	3 Months Ended
Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Note 1 - Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals, considered necessary for a fair presentation have been included. All share and per share data have been restated to give effect to the 10% stock dividend issued on December 15, 2017. Certain amounts in prior-period financial statements have been reclassified to conform to the current period’s presentation. For further information, refer to the audited consolidated financial statements and related footnotes included in Cass Information System, Inc.’s (the “Company” or “Cass”) Annual Report on Form 10-K for the year ended December 31, 2017. On January 1, 2018, the Company adopted accounting standard ASC 606, Revenue from Contracts with Customers, and selected the modified retrospective transition method. The adoption of this new standard did not impact the Company’s results of operations or balance sheet and there was no cumulative effect of initially applying this new revenue standard to the opening balance of retained earnings. Since interest income on loans and securities are both excluded from this topic, a significant portion of the Company’s revenues are not subject to the new guidance. The services that fall within the scope of ASC 606 are presented within fee revenue and other income in the Consolidated Statements of Income and are recognized as revenue as the obligation to the customer is satisfied. Services within the scope of ASC 606 include transportation and facility payment and processing fees, bank service fees, and other real estate owned (“OREO”). Transportation and facility payment and processing fees – The Company earns fees on a per-item basis for the services rendered on behalf of customers. Fees are earned over the course of a month, representing the period over with the performance obligation is satisfied. Bank service fees – Revenue from service fees consists of service charges and fees on deposit accounts under depository agreements with customers to provide access to deposited funds and, when applicable, pay interest on deposits. Service charges on deposit accounts are primarily all charges that are recognized on a monthly basis representing the period over which the performance obligation is satisfied. OREO – The Company currently does not have any OREO and has not in recent years. Net gains or losses would be recorded when other real estate is sold to a third party and substantially all of the consideration for the transfer of property is received.

Basis of Presentation

3 Months Ended

Mar. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Note 1 - Basis of Presentation

The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments, consisting of normal recurring accruals, considered necessary for a fair presentation have been included. All share and per share data have been restated to give effect to the 10% stock dividend issued on December 15, 2017. Certain amounts in prior-period financial statements have been reclassified to conform to the current period’s presentation. For further information, refer to the audited consolidated financial statements and related footnotes included in Cass Information System, Inc.’s (the “Company” or “Cass”) Annual Report on Form 10-K for the year ended December 31, 2017.

On January 1, 2018, the Company adopted accounting standard ASC 606, Revenue from Contracts with Customers, and selected the modified retrospective transition method. The adoption of this new standard did not impact the Company’s results of operations or balance sheet and there was no cumulative effect of initially applying this new revenue standard to the opening balance of retained earnings. Since interest income on loans and securities are both excluded from this topic, a significant portion of the Company’s revenues are not subject to the new guidance. The services that fall within the scope of ASC 606 are presented within fee revenue and other income in the Consolidated Statements of Income and are recognized as revenue as the obligation to the customer is satisfied. Services within the scope of ASC 606 include transportation and facility payment and processing fees, bank service fees, and other real estate owned (“OREO”).

Transportation and facility payment and processing fees – The Company earns fees on a per-item basis for the services rendered on behalf of customers. Fees are earned over the course of a month, representing the period over with the performance obligation is satisfied.

Bank service fees – Revenue from service fees consists of service charges and fees on deposit accounts under depository agreements with customers to provide access to deposited funds and, when applicable, pay interest on deposits. Service charges on deposit accounts are primarily all charges that are recognized on a monthly basis representing the period over which the performance obligation is satisfied.

OREO – The Company currently does not have any OREO and has not in recent years. Net gains or losses would be recorded when other real estate is sold to a third party and substantially all of the consideration for the transfer of property is received.