Gains and Losses on Derivatives Designated as Hedging Instruments, Cash Flow Hedging (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Interest Expense [Member] | Interest Rate Swap [Member]
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) Recognized in Income on Derivative (Ineffective Portion and Amount Excluded from Effectiveness Testing)	$ 4.1	$ 2.0	$ 7.6	$ 0.5