SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash and Cash Equivalents
Outstanding checks in excess of funds on deposits	$ 19.8	$ 19.6
Accounts Receivable
Deposits to the CCF by way of assigned eligible accounts receivable	112.0
Allowance for doubtful accounts
Balance at Beginning of year	4.7	5.3	6.1
Expense	0.6	0.7
Write-offs and Other	(1.2)	(1.3)	(0.8)
Balance at End of Year	4.1	4.7	5.3
Prepaid and Other Assets:
Prepaid expenses and other assets includes diesel and heavy fuel oil expense that is primarily aboard the company's vessels	13.8	17.9
Carrying value
Fair value of financial instruments
Cash and cash equivalents	114.5	19.9
Accounts and notes receivable, net	182.3	174.7
Variable rate debt		24.0
Fixed rate debt	286.1	295.1
Fair value
Fair value of financial instruments
Cash and cash equivalents	114.5	19.9
Accounts and notes receivable, net	182.3	174.7
Variable rate debt		24.0
Fixed rate debt	292.7	316.8
Fair value | Quoted Prices in Active Markets (Level 1)
Fair value of financial instruments
Cash and cash equivalents	114.5	19.9
Fair value | Significant Observable Inputs (Level 2)
Fair value of financial instruments
Accounts and notes receivable, net	182.3	174.7
Variable rate debt		24.0
Fixed rate debt	$ 292.7	$ 316.8