ACQUISITIONS (Bison Midstream) (Details) (USD $)
 12 Months Ended 0 Months Ended 12 Months Ended 0 Months Ended 12 Months Ended 0 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2013
Gas Gathering Contract
Minimum
Dec. 31, 2013
Gas Gathering Contract
Maximum
Jun. 04, 2013
Bison Midstream
Dec. 31, 2013
Bison Midstream
Feb. 15, 2013
Bison Midstream
Jun. 04, 2013
Bison Midstream
Limited partners, Common
Jun. 04, 2013
Bison Midstream
General Partner Units
Jun. 04, 2013
Bison Midstream
SMP Holdings' equity in Bison Midstream
Dec. 31, 2013
Bison Midstream
SMP Holdings' equity in Bison Midstream
Jun. 04, 2013
Bison Midstream
Weighted Average
Jun. 04, 2013
Bison Midstream
Gas Gathering Contract
Minimum
Jun. 04, 2013
Bison Midstream
Gas Gathering Contract
Maximum
Business Acquisition [Line Items]                              
Cost of acquired entity, purchase price           $ 248,900,000         $ 248,900,000        
Useful lives       10 years 25 years               12 years 5 years 15 years
Cost of acquired entity, cash paid           200,000,000         200,000,000        
Cost of acquired entity, equity interests issued and issuable                 47,900,000 1,000,000          
Purchase price assigned to Bison Gas Gathering system             303,168,000       303,200,000 303,168,000      
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]                              
Purchase price assigned to Bison Gas Gathering system               303,168,000              
Current assets               5,705,000              
Property, plant, and equipment               85,477,000              
Intangible assets               164,502,000              
Other noncurrent assets               2,187,000              
Total assets acquired               257,871,000              
Current liabilities               6,112,000              
Other noncurrent liabilities               2,790,000              
Total liabilities assumed               8,902,000              
Net identifiable assets acquired               248,969,000              
Goodwill $ 115,888,000 $ 45,478,000 $ 45,478,000       $ 54,200,000 $ 54,199,000