Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, allowance for doubtful accounts	$ 0	$ 0
Property, plant and equipment, accumulated depreciation	125,834	117,067
Intangible assets, accumulated amortization	$ 10,500	$ 10,300
Common Units-Public
Limited partner units issued	13,179,815	13,073,439
Limited partner units outstanding	13,179,815	13,073,439
Common Units-Sponsor
Limited partner units issued	1,265,453	1,347,161
Limited partner units outstanding	1,265,453	1,347,161
Subordinated Units-Sponsor
Limited partner units issued	11,905,138	11,905,138
Limited partner units outstanding	11,905,138	11,905,138
General Partner
General partner units outstanding	0	0