Note 2 - Net Profits Interest Divestiture (Details Textual) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Mar. 31, 2021
Net Profits Interests Divestiture, Consideration	$ 5.7
Trade and Other Receivables [Member]
Net Profits Interests Divestiture, Consideration, Holdbacks		$ 0.2

Amount of consideration received or receivable for net profits interest divestiture.

No definition available.

Name:	dmlp_NetProfitsInterestsDivestitureConsideration
Namespace Prefix:	dmlp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration