Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue from contract with customer	$ 308,915	$ 316,807
Total revenue	371,070	384,835	[1]
Operating expense	103,289	113,890
General and administrative expense	14,095	15,995
Asset impairment expense	2,476	53,068
Total costs and expenses	337,341	412,198
Gain on sale of assets	453	149
Operating income (loss)	34,182	(27,214)	[2]
Other income (expenses):
Other income	268
Gain on sale of unconsolidated affiliate		2,225
Interest expense	(15,975)	(16,860)
Income (loss) before income taxes	18,475	(41,849)
Provision for income taxes	63	198
Net income (loss)	18,412	(42,047)	[2]
Allocation of net income (loss) for calculation of earnings per unit:
General partner interest in net income (loss)	337	(512)
Preferred interest in net income	25,115	25,115
Net loss available to limited partners	$ (7,040)	$ (66,650)
Basic and diluted net loss per common unit (in dollars per share)	$ (0.17)	$ (1.61)
Weighted average common units outstanding - basic and diluted (in shares)	40,755	40,348
Third Party [Member]
Operating Lease, Lease Income, Total	$ 41,712	$ 42,067
Cost of product sales	83,319	126,776
Related Party [Member]
Operating Lease, Lease Income, Total	20,443	25,961
Cost of product sales	134,162	102,469
Service [Member] | Third Party [Member]
Revenue from contract with customer	61,811	58,756
Service [Member] | Related Party [Member]
Revenue from contract with customer	16,053	22,131
Product [Member] | Third Party [Member]
Revenue from contract with customer	231,051	235,438
Product [Member] | Related Party [Member]
Revenue from contract with customer		$ 482

[1] The increase in revenue during 2018 is due to an increase in volume in the Partnership's crude oil marketing business.

[2] Operating loss and net loss for the fourth quarter and full year 2018 are impacted by asset impairment charges of $52.4 million and $53.1 million, respectively.