cm:Level3TextBlock: us-gaap:ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock
| Schedule of Unrealized Loss on Investments [Table Text Block] |
| us-gaap:ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock |
| For all investments in an unrealized loss position, including those 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), a tabular disclosure of the aggregate related fair value of investments with unrealized losses and the aggregate amount of unrealized losses (that is, the amount by which amortized cost basis exceeds fair value). |
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| For Period (duration) |
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| us-gaap:ScheduleOfUnrealizedLossOnInvestmentsTableTextBlock |
| UnrealizedLossonInvestments |