PARTNERS' CAPITAL AND MEMBERSHIP INTERESTS (Cash Distributions) (Details) (USD $)
0 Months Ended 12 Months Ended 0 Months Ended
Nov. 14, 2013
Aug. 14, 2013
May 15, 2013
Feb. 14, 2013
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Feb. 14, 2014
Subsequent Event
Feb. 14, 2014
General partner
Subsequent Event
Nov. 14, 2013
Limited partners, Common
Aug. 14, 2013
Limited partners, Common
May 15, 2013
Limited partners, Common
Feb. 14, 2013
Limited partners, Common
Feb. 14, 2014
Limited partners, Common
Subsequent Event
Nov. 14, 2013
Subordinated
Aug. 14, 2013
Subordinated
May 15, 2013
Subordinated
Feb. 14, 2013
Subordinated
Feb. 14, 2014
Subordinated
Subsequent Event
Nov. 14, 2013
General Partner Units
Aug. 14, 2013
General Partner Units
May 15, 2013
General Partner Units
Feb. 14, 2013
General Partner Units
Feb. 14, 2014
General Partner Units
Subsequent Event
Distribution Made to Limited Partner [Line Items]                                                
Per-unit distribution $ 0.46 $ 0.435 $ 0.42 $ 0.41       $ 0.48                                
Distributions to unitholders $ 25,108,000 $ 23,740,000 $ 20,923,000 $ 20,425,000 $ 90,196,000 $ 0 $ 0 $ 26,366,000   $ 13,377,000 $ 12,647,000 $ 10,253,000 $ 10,009,000 $ 13,958,000 $ 11,229,000 $ 10,618,000 $ 10,252,000 $ 10,008,000 $ 11,717,000 $ 502,000 $ 475,000 $ 418,000 $ 408,000 $ 691,000
General partner's IDRs                 $ 163,000