SIGNIFICANT ACCOUNTING POLICIES - FISCAL YEAR (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Fiscal Year
Fiscal Period Duration	364 days	364 days	364 days
Cash and Cash Equivalents
Outstanding checks in excess of funds on deposits	$ 13.8	$ 18.9
Accounts Receivable
Eligible accounts receivable assigned to CCF	176.6	150.7
Allowance for doubtful accounts
Balance at Beginning of year	5.0	4.1	$ 4.7
Expense	2.0	1.8	0.6
Write-offs and Other	(0.4)	(0.9)	(1.2)
Balance at End of Year	6.6	5.0	$ 4.1
Prepaid and Other Assets:
Prepaid fuel	9.3	11.0
Insurance	4.9	2.9
Income tax receivable	15.1
Other	8.8	6.6
Total	38.1	20.5
Carrying value
Cash and Cash Equivalents
Cash and cash equivalents	25.5	293.4
Accounts receivable, net	214.3	197.6
Fixed rate debt	429.9	373.6
Fair Value Measurement
Cash and Cash Equivalents
Cash and cash equivalents	25.5	293.4
Accounts receivable, net	214.3	197.6
Fixed rate debt	443.8	395.7
Fair Value Measurement | Quoted Prices in Active Markets (Level 1)
Cash and Cash Equivalents
Cash and cash equivalents	25.5	293.4
Fair Value Measurement | Significant Observable Inputs (Level 2)
Cash and Cash Equivalents
Accounts receivable, net	214.3	197.6
Fixed rate debt	$ 443.8	$ 395.7