Subsequent Events (Details) - Subsequent Event [Member]	1 Months Ended
Oct. 24, 2017 $ / shares
10% Common Stock Dividend [Member]
Subsequent Event [Line Items]
Dividend declaration date	Oct. 24, 2017
Dividend payable date	Dec. 15, 2017
Dividend record date	Dec. 05, 2017
Dividend description	Shareholders will receive one additional share of Cass common stock for each 10 shares of common stock owned. No fractional shares will be issued. Shareholders will receive cash for any fractional shares owned based on the share price reported by the Nasdaq Stock Market at the close of trading on December 5, 2017.
Cash Dividend [Member]
Subsequent Event [Line Items]
Dividend per share	$ 0.24
Dividend declaration date	Oct. 24, 2017
Dividend payable date	Dec. 15, 2017
Dividend record date	Dec. 05, 2017

Date the declared dividend will be paid, in CCYY-MM-DD format.

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- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

+ Details

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- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

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- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

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- Definition

Describes the declaration as being a special dividend (over and above the normal dividend); as the annual, semi-annual, quarterly dividend, or other normal periodic dividend; or as some other type of dividend.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

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- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

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