Note 7 - Series A Preferred Units (Details Textual) - USD ($)				4 Months Ended	12 Months Ended
		Feb. 08, 2017	Aug. 31, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Proceeds from Issuance of Preferred Limited Partners Units						$ 85,954,000
Payments for Offering Costs for Preferred Units						2,250,000
Interest Expense, Related Party	[1]				21,855
Series A Preferred Units [Member]
Proceeds from Issuance of Preferred Limited Partners Units			$ 90,000,000
Net Proceeds from Issuance of Preferred Limited Partners Units			83,700,000
Payments for Offering Costs for Preferred Units			2,200,000
Interest Expense, Related Party			$ 4,000,000
Preferred Unit, Annual Cash Distribution Percentage				10.50%
Temporary Equity, Accretion to Redemption Value				$ 777,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid					$ 1,500,000	$ 3,900,000
Temporary Equity, Period of Redemption					3 years
Series A Preferred Units [Member] | IPO [Member]
Stock Issued During Period, Shares, Conversion of Units		12,764,426

[1] Adjustment has been made to the loss to add back interest expense associated with the note payable to Ramaco Coal, LLC which was repaid in full using proceeds from the IPO.