CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Property and equipment, Accumulated depreciation	$ 61.4	$ 60.3
Common stock, shares authorized	180,000,000us-gaap_CommonStockSharesAuthorized	180,000,000us-gaap_CommonStockSharesAuthorized
Common stock, issued	92,322,905us-gaap_CommonStockSharesIssued	92,322,905us-gaap_CommonStockSharesIssued
Common stock, outstanding	92,302,636us-gaap_CommonStockSharesOutstanding	92,302,636us-gaap_CommonStockSharesOutstanding
Treasury stock, shares	20,269us-gaap_TreasuryStockShares	20,269us-gaap_TreasuryStockShares

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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