Income Taxes - Deferred Taxes in Consolidated Balance Sheets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Current assets	$ 56.2us-gaap_DeferredTaxAssetsNetCurrent	$ 59.5us-gaap_DeferredTaxAssetsNetCurrent
Non-current assets	304.1us-gaap_DeferredTaxAssetsNetNoncurrent	303.6us-gaap_DeferredTaxAssetsNetNoncurrent
Current liabilities	0us-gaap_DeferredTaxLiabilitiesCurrent	0us-gaap_DeferredTaxLiabilitiesCurrent
Other non-current liabilities	(9.4)	(15.1)
Net deferred tax assets	$ 350.9us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 348.0us-gaap_DeferredTaxAssetsLiabilitiesNet

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

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- Definition

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 within one year or operating cycle, if longer.

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