MEMBERS' EQUITY Table 3 (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended				12 Months Ended
	Jan. 29, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Distribution Made to Limited Liability Company (LLC) Member [Line Items]
Cash distributions per unit applicable to members (distribution earned)		$ 0.545	$ 0.545	$ 0.545	$ 0.545	$ 2.18	$ 2.18	$ 2.18
Total cash distributions (distribution earned)		$ 23,423	$ 23,409	$ 23,408	$ 23,409	$ 93,649	$ 93,601	$ 93,561
Distribution date of record (distribution earned)		Feb. 08, 2018	Nov. 09, 2017	Aug. 07, 2017	May 08, 2017
Distribution payment date (distribution earned)		Feb. 15, 2018	Nov. 16, 2017	Aug. 15, 2017	May 16, 2017
Subsequent Event [Member]
Distribution Made to Limited Liability Company (LLC) Member [Line Items]
Distribution announcement date (distribution earned)	Jan. 29, 2018