| Standard label: | Schedule of Auction Market Preferred Securities by Stock Series [Table Text Block] |
| Name: | us-gaap:ScheduleOfAuctionMarketPreferredSecuritiesByStockSeriesTextBlock |
| Documentation: | Tabular disclosure of information pertaining to auction market preferred securities, including liquidation preference, liquidation value, par value, rate setting interval, redemption requirements, dividend distributions, roll forward of shares outstanding, shares authorized, aggregate value of auction market preferred securities, variable interest rate earned, and other information necessary to a fair presentation. If redeemable, the auction market preferred securities are redeemable solely at the option of the issuer. |
| Object type: | cm:Level3TextBlock |
| 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:ScheduleOfAuctionMarketPreferredSecuritiesByStockSeriesTextBlock |
| Examples of this text block disclosure: | AuctionMarketPreferredSecuritiesByStockSeries |
| Label | Role | Language |
| Schedule of Auction Market Preferred Securities by Stock Series [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 210 10 S99 1 (SX 210.5-02(28)) | http://fasb.org/us-gaap/role/ref/legacyRef | 210 |
| FASB Accounting Standards Codification 505 10 50 3 | http://fasb.org/us-gaap/role/ref/legacyRef | 505 |
| FASB Accounting Standards Codification 505 10 50 4 | http://fasb.org/us-gaap/role/ref/legacyRef | 505 |
| FASB Accounting Standards Codification 505 10 50 5 | http://fasb.org/us-gaap/role/ref/legacyRef | 505 |
| FASB Accounting Standards Codification 505 10 50 11 | http://fasb.org/us-gaap/role/ref/legacyRef | 505 |