Derivatives - Effect of Our Derivative Financial Instruments on Our Consolidated Statements of Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivatives in cash flow hedging relationships:
Gain (loss) recognized in Other Comprehensive Income (Loss) on derivatives	$ 1.4	$ 0.3	$ (0.7)	$ 7.9
Interest
Derivatives in cash flow hedging relationships:
Loss reclassified from Accumulated Other Comprehensive Income (Loss) into income (effective portion)	1.0	2.0	3.3	9.0
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)	$ (0.1)	$ (0.7)	$ (1.4)	$ (3.4)