Schedule of Gains (Losses) for Derivatives Designated as Fair Value Hedges (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Total gain recognized as ineffectiveness in the condensed consolidated statements of operations	$ (1.3)	$ (1.2)	$ (2.1)
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total gain recognized as ineffectiveness in the condensed consolidated statements of operations	(5.7)	(3.1)	(16.8)
Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Total gain recognized as ineffectiveness in the condensed consolidated statements of operations	$ 4.4	$ 1.9	$ 14.7