Debt - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Debt Narrative Detail Information
Amount Outstanding on Revolving Credit Facility	$ 0.0
Payments of Debt Extinguishment Costs	0.0	$ 13.2
Northwind Holdings LLC
Debt Narrative Detail Information
Principal Payments on Long-term Debt	$ 48.4
Notes Issued in 2005
Debt Narrative Detail Information
Interest Rate on Debt Instrument	6.85%
Long-term Debt
Debt Narrative Detail Information
Interest Rate on Debt Instrument		6.85%
Extinguishment of Debt, Amount		$ 145.0
Payments of Debt Extinguishment Costs		13.2
Repayment of Long-term Debt, Including Cost of Make-whole Call Premium		158.2
Hedge Gain Reclassification from AOCI to Earnings		$ 13.1

[Line Items] for Debt Narrative Detail Information

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- Definition

Repayment of Long-term Debt, Including Cost of Make-whole Call Premium

+ References

No definition available.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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- Definition

Amount of the required periodic payments applied to principal.

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-SubTopic 10

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- Definition

Gross amount of debt extinguished.

+ References

No definition available.

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- Definition

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.

+ References

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-Publisher FASB

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-Topic 942

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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- Definition

Amount before tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

+ References

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-Publisher FASB

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-Section 50

-Paragraph 4

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- Definition

The cash outflow for incremental, external costs directly pertaining to an early extinguishment of debt, including legal costs and prepayment penalties, and excluding interest and repayment of debt principal.

+ References

No definition available.

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