| Standard label: | Auction Market Preferred Securities, Stock Series, Liquidation Value |
| Name: | us-gaap:AuctionMarketPreferredSecuritiesStockSeriesLiquidationValue |
| Documentation: | The amount of the liquidation value for auction market preferred securities. |
| Object type: | cm:Concept |
| Data type: | Monetary (xbrli:monetaryItemType) |
| Period type: | As Of (instant) |
| Balance type: | Credit |
| Abstract: | false |
| Workiva Wdesk Taxonomy Analyzer: | us-gaap:AuctionMarketPreferredSecuritiesStockSeriesLiquidationValue |
| Label | Role | Language |
| Auction Market Preferred Securities, Stock Series, Liquidation Value | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 235 10 S99 1 (SX 210.4-08.(d)) | http://fasb.org/us-gaap/role/ref/legacyRef | 235 |
| FASB Accounting Standards Codification 505 10 50 4 | http://fasb.org/us-gaap/role/ref/legacyRef | 505 |