Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Total revenues	$ 82,387	$ 100,748	$ 106,993
Operating expenses
Operations and maintenance (excluding depreciation and amortization reflected below)	25,658	30,866	33,501
General and administrative	4,055	5,258	4,223
Depreciation and amortization	3,441	4,442	5,111
Gain on assignment of operating leases		(2,721)
Total operating expenses	33,154	37,845	42,835
Operating income	49,233	62,903	64,158
Other income (expense)
Interest income	81	81	81
Interest expense	(8,310)	(7,307)	(5,402)
Other, net	14	119	150
Total other expense	(8,215)	(7,107)	(5,171)
Income before income taxes and income (loss) from equity method investee	41,018	55,796	58,987
Income tax expense	(220)	(101)	(109)
Income (loss) from equity method investee	681	(14)	(11)
Net income	41,479	55,681	58,867
Net income attributable to partners' ownership interests	41,479	55,681	58,867
Affiliate [Member]
Revenues
Total revenues	75,531	94,267	100,808
Non-affiliate [Member]
Revenues
Total revenues	6,856	6,481	6,185
General Partner [Member]
Other income (expense)
Net income	830	1,114	1,177
Net income attributable to partners' ownership interests	830	1,114	1,177
Limited Partners [Member] | Common Units [Member]
Other income (expense)
Net income attributable to partners' ownership interests	$ 40,649	$ 37,868	$ 28,869
Earnings per limited partner unit (basic and diluted):
Earnings per limited partner unit (basic and diluted)	$ 1.76	$ 1.81	$ 1.81
Weighted average limited partner units outstanding (basic and diluted):
Weighted average limited partner units outstanding (basic and diluted)	23,129,000	20,950,000	15,916,000
Limited Partners [Member] | Subordinated Units [Member]
Other income (expense)
Net income		$ 16,699	$ 28,821
Net income attributable to partners' ownership interests		$ 16,699	$ 28,821
Earnings per limited partner unit (basic and diluted):
Earnings per limited partner unit (basic and diluted)		$ 1.71	$ 1.81
Weighted average limited partner units outstanding (basic and diluted):
Weighted average limited partner units outstanding (basic and diluted)		9,752,000	15,890,000