MEMBERS' EQUITY Table 1 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Our cash distributions applicable to the period in which the distributions were earned
Cash distributions per unit	$ 0.545	$ 0.545	$ 0.510	$ 0.510	$ 0.510	$ 0.495	$ 0.495	$ 0.480	$ 2.110	$ 1.980	$ 1.87
Total cash distributions									$ 89,860	$ 84,252	$ 79,517