| Standard label: | Schedule of Aging of Capitalized Exploratory Well Costs [Table Text Block] |
| Name: | us-gaap:ScheduleOfAgingOfCapitalizedExploratoryWellCostsTextBlock |
| Documentation: | Tabular disclosure of the amount of exploratory well costs that have been capitalized after the completion of drilling and the number of projects for which those costs relate. Additionally, for exploratory well costs that have been capitalized for periods greater than one year at the most recent balance sheet date, this block of text may be used to disclose an aging of those amounts by year, or by using a range of years, and the number of projects to which those costs relate. |
| 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:ScheduleOfAgingOfCapitalizedExploratoryWellCostsTextBlock |
| Label | Role | Language |
| Schedule of Aging of Capitalized Exploratory Well Costs [Table Text Block] | http://www.xbrl.org/2003/role/label | en-US |
| Reference | Role | Topic |
| FASB Accounting Standards Codification 932 235 50 1B (b) | http://fasb.org/us-gaap/role/ref/legacyRef | 932 |