Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Debt Narrative Detail Information
Amount Outstanding on Revolving Credit Facility	$ 0
Gross Proceeds from Issuance of Long-term Debt	350.0
Repayments of Long-term Debt	15.0	71.2
Northwind Holdings LLC
Debt Narrative Detail Information
Periodic Principal Payments on Long-term Debt	15.0
Tailwind Holdings LLC
Debt Narrative Detail Information
Repayments of Long-term Debt		62.5
Gain on Extinguishment of Debt		4.0
Debt Issued in the First Quarter of 2014
Debt Narrative Detail Information
Interest Rate on Debt	4.00%
Subsequent Event
Debt Narrative Detail Information
Repayments of Long-term Debt	$ 145.0
Debt to be Redeemed in the Second Quarter of 2014
Debt Narrative Detail Information
Interest Rate on Debt	6.85%