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	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Loss Recognized on Swap	$ (1.1)	$ (0.9)	$ (2.1)	$ (1.9)
Gain Recognized on Long-Term Debt	$ 1.1	$ 0.9	$ 2.1	$ 1.9