MEMBERS' EQUITY Table 4 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended			0 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Apr. 22, 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
Total cash distributions (distribution earned)	$ 23,388	$ 23,403	$ 23,248
Distribution date of record (distribution earned)	May 08, 2015	Feb. 09, 2015
Distribution payment date (distribution earned)	May 18, 2015	Feb. 17, 2015
Subsequent Event [Member]
Distribution Made to Limited Liability Company (LLC) Member [Line Items]
Distribution announcement date (distribution earned)				Apr. 22, 2015