Consolidated Balance Sheets (Parenthetical) - shares	Mar. 31, 2018	Dec. 31, 2017
Common units [Member] | Public [Member]
Units issued	18,115,036	18,112,500
Units outstanding	18,115,036	18,112,500
Common units [Member] | Westlake [Member]
Units issued	14,122,230	14,122,230
Units outstanding	14,122,230	14,122,230
Subordinated units [Member] | Westlake [Member]
Units issued	0	0
Units outstanding	0	0