Location and Amounts of Gains and Losses on Derivative Instrument Designated as Fair Value Hedge (Detail) (Interest rate swap contract, Interest Expense, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest rate swap contract | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
(Loss)/Gain Recognized on Swap	$ (0.3)	$ 1.0	$ (3.5)	$ 2.5
Gain/Loss Recognized on Long-Term Debt	$ 0.3	$ (1.0)	$ 3.5	$ (2.5)