Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2018	Dec. 31, 2017
Series A Preferred Stock [Member]
Partners' capital:
Limited partner interest, units issued (in shares)	0	12,000,000
Limited partner interest, units outstanding (in shares)	0	12,000,000
Common Units - Public [Member]
Partners' capital:
Limited partner interest, units issued (in shares)	54,201,090	53,917,173
Limited partner interest, units outstanding (in shares)	54,201,090	53,917,173
Common Units Affiliated [Member]
Partners' capital:
Limited partner interest, units issued (in shares)	28,463,967	45,750,826
Limited partner interest, units outstanding (in shares)	28,463,967	45,750,826
Class C Units Subsidiary [Member]
Partners' capital:
Limited partner interest, units issued (in shares)	16,410,780	16,410,780
Limited partner interest, units outstanding (in shares)	16,410,780	16,410,780