EQUITY INVESTMENTS - Equity Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Equity investments
Total earnings from equity investments	$ 3,088	$ 2,134
West Shore Pipe Line Company
Equity investments
Total earnings from equity investments	2,331	1,778
Muskegon Pipeline LLC
Equity investments
Total earnings from equity investments	377	87
Transport4, LLC
Equity investments
Total earnings from equity investments	147	(32)
South Portland Terminal LLC
Equity investments
Total earnings from equity investments	$ 233	$ 301