MEMBERS' EQUITY Table 2 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Our cash distributions applicable to the period in which the distributions were earned
Cash distributions per unit	$ 0.545	$ 0.545	$ 0.545	$ 0.545	$ 2.18	$ 2.18	$ 2.18
Total cash distributions	$ 23,423	$ 23,409	$ 23,408	$ 23,409	$ 93,649	$ 93,601	$ 93,561