Derivatives - Effect of Our Derivative Financial Instruments on Our Consolidated Statements of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivatives in cash flow hedging relationships:
Loss recognized in Other Comprehensive Income (Loss) on derivatives	$ 0.2	$ (0.3)	$ (1.6)	$ (2.2)
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)			0.5
Interest
Derivatives in cash flow hedging relationships:
Loss reclassified from Accumulated Other Comprehensive Income (Loss) into income (effective portion)	$ 1.2	1.2	2.3	2.2
Loss recognized in income on derivatives (ineffective portion and amount excluded from effectiveness testing)		$ (1.2)	$ (0.5)	$ (1.2)