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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Interest rate swaps [Member] | Interest expense [Member]
Derivatives And Hedging Activities [Line Items]
Gain / (Loss) on Instrument	$ (4.9)	$ (1.6)	$ 7.0	$ (15.7)
Gain / (Loss) on Hedged Item	$ 4.9	$ 1.6	$ (7.0)	$ 15.7