cm:Concept: us-gaap:ClosedBlockDividendObligationIncreaseDecreaseForEffectOfOperatingResults
| Closed Block Dividend Obligation, Increase (Decrease) for Effect of Operating Results |
| us-gaap:ClosedBlockDividendObligationIncreaseDecreaseForEffectOfOperatingResults |
| Amount of increase (decrease) in the closed block dividend obligation from the effect on dividends to policyholders on the net results of operations for the period of the closed block. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:ClosedBlockDividendObligationIncreaseDecreaseForEffectOfOperatingResults |