GOODWILL AND INTANGIBLE ASSETS - Changes in Carrying Amount of Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill
Impairment of long lived assets	$ 0
Impairments of equity investments	300,300,000	$ 0	$ 0
Changes in the carrying amount of goodwill
Balance at the beginning of the period	1,007,313,000	1,004,545,000
Acquisition		2,768,000
Purchase price adjustments	526,000
Impairment of goodwill	(536,964,000)	0	0
Balance at the end of the period	470,875,000	1,007,313,000	1,004,545,000
Domestic Pipelines & Terminals
Changes in the carrying amount of goodwill
Balance at the beginning of the period	298,471,000	295,703,000
Acquisition		2,768,000
Purchase price adjustments	526,000
Impairment of goodwill	0
Balance at the end of the period	298,997,000	298,471,000	295,703,000
Merchant Services
Changes in the carrying amount of goodwill
Balance at the beginning of the period	4,499,000	4,499,000
Acquisition		0
Purchase price adjustments	0
Impairment of goodwill	0
Balance at the end of the period	4,499,000	4,499,000	4,499,000
GMT Caribbean and NYH
Changes in the carrying amount of goodwill
Balance at the beginning of the period	536,964,000	536,964,000
Acquisition		0
Purchase price adjustments	0
Impairment of goodwill	(536,964,000)
Balance at the end of the period	0	536,964,000	536,964,000
GMT South Texas
Changes in the carrying amount of goodwill
Balance at the beginning of the period	167,379,000	167,379,000
Acquisition		0
Purchase price adjustments	0
Impairment of goodwill	0
Balance at the end of the period	$ 167,379,000	$ 167,379,000	$ 167,379,000