INVESTMENT IN TERMINAL JOINT VENTURE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments in affiliates
Investment in related party Terminal Joint Venture	$ 82.4	$ 66.4
Financial information for equity method investment
Company Share of Net Income	15.8	16.5	$ 6.6
Distributions Received		14.0
Current assets	147.7	107.0
Noncurrent assets	138.5	121.2
Total assets	286.2	228.2
Current liabilities	48.9	42.0
Noncurrent liabilities	14.8	9.4
Equity	222.5	176.8
Total Liabilities and Equity	286.2	228.2
Operating revenue	740.9	621.0	586.2
Operating costs and expenses	706.5	610.2	589.7
Operating Income (loss)	34.4	10.8	(3.5)
Net Income	$ 45.1	44.9	21.2
SSAT | Ocean Transportation
Investments in affiliates
Ownership interest accounted in the related party terminal joint venture (as a percent)	35.00%
Cost of services from transactions with unconsolidated affiliate	$ 177.8	174.1	$ 164.8
Accounts payable and accrued liabilities	$ 16.7	$ 19.5