UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Series A preferred unitholders, issued	300,000	300,000
Series A preferred unitholders, outstanding	300,000	300,000
Common limited partner capital (in shares), issued	73,355,775	73,085,996
Common limited partner capital (in shares), outstanding	73,355,775	73,085,996
General partner interests (in shares), issued	1,490,999	1,490,999
General partner interests (in shares), outstanding	1,490,999	1,490,999