CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares shares in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Series A preferred unitholders, issued	300
Series A preferred unitholders, outstanding	300
Common limited partner capital (in shares), issued	73,086	72,111
Common limited partner capital (in shares), outstanding	73,086	72,111
General partner interests (in shares), issued	1,491	1,471
General partner interests (in shares), outstanding	1,491	1,471