ACQUISITIONS - Purchase Price Allocation to Tangible and Intangible Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	May. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 998,659	$ 998,748
Pennsauken Pipeline
Business Acquisition [Line Items]
Property, plant and equipment		5,287
Goodwill		2,372
Environmental liabilities		(2,372)
Allocated purchase price		$ 5,287
ExxonMobil Pipeline
Business Acquisition [Line Items]
Property, plant and equipment			$ 4,040
Goodwill			8,165
Asset retirement obligation			(4,200)
Environmental liabilities			(293)
Allocated purchase price			$ 7,712