Organization, Nature of Business, and Risk and Uncertainties (Details)	9 Months Ended
Sep. 30, 2020
Organization, Nature of Business, and Risk and Uncertainties
Number of months cash and Investments sufficient to fund operating and capital expenditure	12 months

The number of months the cash and investments would be sufficient to fund operating and capital expenditure.

No definition available.

Name:	dmi_NumberOfMonthsCashAndInvestmentsSufficientToFundOperatingAndCapitalExpenditure
Namespace Prefix:	dmi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration