Debt - Additional Information Domain (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Repayments of Long-term Debt	$ 71.2	$ 17.5
Northwind Holdings LLC [Member]
Debt Instrument, Periodic Payment, Principal	15.0
Tailwind Holdings LLC [Member]
Repayments of Long-term Debt	62.5
Gains (Losses) on Extinguishment of Debt	$ 4.0
Securities Pledged as Collateral [Member]
Short-term Debt, Description	entirely

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References+ Details

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References+ Details

- Definition

Information about borrowings which initially required repayment in less than twelve months (or normal operating cycle, if longer) after its issuance and that does not otherwise qualify as long-term debt. It typically is comprised of borrowings under letters of credit, lines of credit, commercial paper, and notes payable of short duration. Disclosures include amounts of borrowings under each arrangement, description of underlying arrangements, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements such as the effects of refinancings and noncompliance with debt covenants.

+ References+ Details