Fair Value Disclosure - Comprehensive Income (Loss) Impacts of Parent Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ (1.3)	$ 0.4	$ (3.9)	$ (0.3)
Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive income (loss) (effective portion)	0.3	0.8	1.0	(5.1)
Cash Flow Hedges [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated unrealized loss on derivative instrument	(1.1)	(2.1)	(4.1)	(6.0)
Cash Flow Hedges [Member] | Operating Lease Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount reclassified from accumulated unrealized loss on derivative instrument	(0.4)	(0.4)	(1.1)	(1.2)
Not designated as hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other expense	$ (2.1)	$ 2.6	$ (0.6)	$ 2.3