cm:Concept: us-gaap:FairValueOptionEventsTriggeringElectionReasons
| Fair Value, Option, Events Triggering Election, Reasons |
| us-gaap:FairValueOptionEventsTriggeringElectionReasons |
| This item represents information describing the nature of certain events which have occurred and thereby allow the fair value option to be elected for a previously ineligible item. Such events may consist of: (1) (a) an investment becoming subject to the equity method of accounting (for example, an investment may previously had been reported as a security categorized as trading or available-for-sale and the level of investment has increased sufficiently to mandate the equity method of accounting) or (b) a subsidiary or variable interest entity ceases to be consolidated but a continuing interest is retained (for example, a majority voting interest is no longer held but the Company continues to hold some common stock); or (2) an event that requires an eligible item to be measured at fair value at the time of the event but does not require fair value measurement at each reporting date after that, excluding the recognition of impairment under lower-of-cost-or-market accounting or other-than-temporary impairment. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:FairValueOptionEventsTriggeringElectionReasons |