| Standard label: | Grandfathered ESOP Expense Recognition, Policy [Policy Text Block] |
| Name: | us-gaap:GrandfatheredESOPExpenseRecognitionPolicy |
| Documentation: | Disclosure of accounting policy for grandfathered ESOP shares acquired prior to January 1, 1993, including the method of measuring compensation, method of recognizing expense, the classification of dividends on ESOP shares, impact of the ESOP on the financial statements and the treatment of ESOP shares for earnings per share computations. |
| Object type: | cm:Level2TextBlock |
| Data type: | Text Block (HTML) (nonnum:textBlockItemType) |
| Period type: | For Period (duration) |
| Balance type: | (no balance type) |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:GrandfatheredESOPExpenseRecognitionPolicy |
| Label | Role | Language |
| Grandfathered ESOP Expense Recognition, Policy [Policy Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 235 10 50 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 235 |
| FASB Accounting Standards Codification 718 40 50 1 (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 718 |