External Debt and Financing Arrangements - Components of External Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
$975 million revolving credit agreement due July 2018	$ 145.0us-gaap_LineOfCredit
$525 million term loan due July 2018	525.0us-gaap_LongTermLoansPayable	350.0us-gaap_LongTermLoansPayable
Total debt	670.0us-gaap_LongTermDebt	350.0us-gaap_LongTermDebt
Less: current portion	26.3us-gaap_LongTermDebtCurrent	0us-gaap_LongTermDebtCurrent
Total long-term debt	643.7us-gaap_LongTermDebtNoncurrent	350.0us-gaap_LongTermDebtNoncurrent
Total debt	$ 670.0us-gaap_LongTermDebt	$ 350.0us-gaap_LongTermDebt

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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