Summary of Components of Interest as Presented in Consolidated Statements of Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Debt Instrument [Line Items]
Income	$ 1.2		$ 1.3		$ 2.5		$ 2.3
Expense on borrowings	(16.4)		(16.3)		(32.8)		(32.7)
Income (expense) on UTPs and other tax related liabilities	(1.5)	[1]	(3.4)	[1]	3.5	[1]	(7.0)	[1]
Legacy Tax			3.7	[2]			3.7	[2]
Capitalized	0.1		0.6		(0.1)		1.4
Total	$ (16.6)		$ (14.1)		$ (26.9)		$ (32.3)

[1] The six months ended June 30, 2012 amount contains a benefit of approximately $7 million related to the settlement of state and local income tax audits.

[2] The 2011 amounts represent a reversal of $2.8 million of accrued interest expense relating to the favorable resolution of a Legacy Tax Matter and $0.9 million of interest income related to a pre-spinoff tax year.