SIGNIFICANT ACCOUNTING POLICIES - PROPERTY AND EQUIPMENT AND OTHER (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Impairment of Investment
Impairment charges related to investment in Terminal joint venture	$ 0.0	$ 0.0	$ 0.0
Capitalized Interest
Interest Costs Capitalized	$ 18.7	$ 7.5	$ 2.1
Dry-docking
Number of dry-docking inspections to be made within a specified period | item	2
Period within which number of specified dry-docking inspections to be made	5 years
Dry-dock inspections interval, minimum	36 months
Vessels
Depreciation
Useful life	40 years
Long-lived Assets
Number of vesels under agreements for contstruction | item	4
Capitalized Interest
Interest Costs Capitalized	$ 12.8
Machinery And Equipment
Depreciation
Useful life	30 years
Terminal Facilities
Depreciation
Useful life	35 years