Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activities - Aggregate Interest Rate Swaps and Fair Value of Liabilities Outstanding (Detail)

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Derivative Instruments and Hedging Activities - Aggregate Interest Rate Swaps and Fair Value of Liabilities Outstanding (Detail) (Interest rate swaps [Member], USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2009
Interest rate swaps [Member]
     
Derivative Instruments, Gain (Loss) [Line Items]      
Aggregate Notional Amounts $ 140.0 $ 140.0  
Average Swap Rate 2.78% 2.78%  
Aggregate Fair Value $ (2.0) $ (5.1)  
Maturity Dates Jul. 31, 2013 Jul. 31, 2013 Jul. 31, 2013