MEMBERS' EQUITY Table 3 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
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	$ 2.11	$ 1.98
Total cash distributions (distribution earned)	$ 23,249	$ 23,231	$ 23,236	$ 23,222	$ 92,938	$ 89,860	$ 84,252
Distribution date of record (distribution earned)	Feb. 10, 2014	Nov. 11, 2013	Aug. 05, 2013	May 06, 2013
Distribution payment date (distribution earned)	Feb. 18, 2014	Nov. 19, 2013	Aug. 14, 2013	May 15, 2013
Distribution announcement date (distribution earned)	Jan. 30, 2014