Income Taxes - Deferred Tax Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Components of Deferred Tax Assets and Liabilities [Abstract]
Income tax benefit related to expiration of statute of limitations for uncertain tax positions and adjustment to prior year's estimates	$ 1.8	$ 0.9
Deferred tax assets:
Employee benefits, including post-retirement benefits	12.4	11.3
Trade and other receivables	4.1	3.6
Goodwill and intangibles	2.6	2.8
Self-insurance reserves	1.2	1.0
Other	3.7us-gaap_DeferredTaxAssetsOther	3.6us-gaap_DeferredTaxAssetsOther
Subtotal	24.0us-gaap_DeferredTaxAssetsGross	22.3us-gaap_DeferredTaxAssetsGross
Less: valuation allowance	(0.1)	(0.1)
Net deferred tax assets	23.9us-gaap_DeferredTaxAssetsNet	22.2us-gaap_DeferredTaxAssetsNet
Deferred tax liabilities:
Inventories	1.3	5.4
Property and equipment	22.6	19.1
Goodwill and intangibles	6.5	7.1
Other	1.6us-gaap_DeferredTaxLiabilitiesOther	1.7us-gaap_DeferredTaxLiabilitiesOther
Total deferred tax liabilities	32.0us-gaap_DeferredIncomeTaxLiabilities	33.3us-gaap_DeferredIncomeTaxLiabilities
Total net deferred tax liabilities	(8.1)us-gaap_DeferredTaxLiabilities	(11.1)us-gaap_DeferredTaxLiabilities
Net current deferred tax assets	8.1	2.3
Net non-current deferred tax liabilities	$ (16.2)	$ (13.4)

Deferred Tax Assets, Trade and other receivables

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Unrecognized Tax Benefits, Reductions Resulting from Lapse of Applicable Statute of Limitations and Adjustment to Prior Years Estimates

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Amount of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets including goodwill.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences expected to be realized or consumed within one year or operating cycle, if longer.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from compensation and benefits costs.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from estimated losses under self insurance.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences net of deferred tax asset attributable to deductible temporary differences and carryforwards after valuation allowances.

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Amount of deferred tax consequences attributable to taxable temporary differences derived from inventory.

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Amount of deferred tax liability attributable to taxable temporary differences, net of deferred tax asset attributable to deductible temporary differences and carryforwards net of valuation allowances expected to be realized or consumed after one year (or the normal operating cycle, if longer).

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Amount of deferred tax liability attributable to taxable temporary differences not separately disclosed.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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