Summary of Restructuring-Related Costs (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
Restructuring Cost and Reserve [Line Items]
Total restructuring and restructuring-related costs	$ 3.0	$ 0.8	$ 2.7	$ 2.1
Charged To Other (Income) Expense, Net | Severance And Other Restructuring Costs
Restructuring Cost and Reserve [Line Items]
Total restructuring and restructuring-related costs	2.9	1.0	4.4	2.2
Charged To Other (Income) Expense, Net | (Gain) Loss From Sale Of Assets
Restructuring Cost and Reserve [Line Items]
Total restructuring and restructuring-related costs	$ 0.1	$ (0.2)	$ (1.7)	$ (0.1)