Derivative Instruments and Hedging Activities - Derivative Instruments Designated as Fair Value Hedges (Detail) (Interest rate swaps [Member], Interest expense [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Interest rate swaps [Member] | Interest expense [Member]
Derivatives And Hedging Activities [Line Items]
Gain / (Loss) on Instrument	$ 6.8	$ (10.8)	$ 11.9	$ (14.1)
Gain / (Loss) on Hedged Item	$ (6.8)	$ 10.8	$ (11.9)	$ 14.1