SIGNIFICANT ACCOUNTING POLICIES - CASH AND ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents
Outstanding checks in excess of funds on deposits	$ 0.0	$ 19.9
Restricted cash	5.3	5.3
Allowance for doubtful accounts
Balance at Beginning of year	6.3	4.3	$ 4.8
Expense	4.2	2.9	0.6
Write-offs and Other	(0.4)	(0.9)	(1.1)
Balance at End of Year	10.1	6.3	$ 4.3
Prepaid and Other Assets:
Income tax receivables	23.1	0.3
Prepaid fuel	22.6	10.8
Prepaid insurance and insurance related receivables	10.1	7.5
Restricted cash - vessel construction obligations	5.3	5.3
Other	17.3	14.2
Total	78.4	38.1
Other Long-term Assets
Vessel and equipment spare parts	12.8	11.5
Insurance related receivables	10.4	10.5
Other	16.2	11.0
Total	$ 39.4	$ 33.0