cm:Level3TextBlock: us-gaap:ScheduleOfTemporaryImpairmentLossesInvestmentsTableTextBlock
| Schedule of Temporary Impairment Losses, Investments [Table Text Block] |
| us-gaap:ScheduleOfTemporaryImpairmentLossesInvestmentsTableTextBlock |
| Tabular disclosure of investments in an unrealized loss position for which other-than-temporary impairments have not been recognized in earnings (including investments for which a portion of an other-than-temporary impairment has been recognized in other comprehensive income), including: (a) the aggregate related fair value of investments with unrealized losses, (b) the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value). |
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| us-gaap:ScheduleOfTemporaryImpairmentLossesInvestmentsTableTextBlock |
| TemporaryImpairmentLossesInvestments |