cm:Member: us-gaap:RevenueFromContractWithCustomerProductAndServiceBenchmarkMember
| Revenue from Contract with Customer, Product and Service Benchmark [Member] |
| us-gaap:RevenueFromContractWithCustomerProductAndServiceBenchmarkMember |
| Revenue from satisfaction of performance obligation by transferring promised product and service to customer for specified product or service, when it serves as benchmark in concentration of risk calculation. |
| cm:Member |
| [Member] (nonnum:domainItemType) |
| For Period (duration) |
| (no balance type) |
| true |
| us-gaap:RevenueFromContractWithCustomerProductAndServiceBenchmarkMember |