Restructuring - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2012 2010 Restructuring And Relocation Program	Jun. 30, 2012 2010 Restructuring And Relocation Program	Jun. 30, 2011 2010 Restructuring And Relocation Program Maximum	Jun. 30, 2011 2010 Restructuring And Relocation Program Maximum	Jun. 30, 2011 2011 Restructuring Program	Jun. 30, 2011 2011 Restructuring Program	Apr. 11, 2011 2011 Restructuring Program Person
Restructuring Cost and Reserve [Line Items]
Number of senior management members entered into separation agreements							4
Restructuring costs incurred	$ 0.1	$ 0.1	$ 0.1	$ 0.3	$ 5.9	$ 10.1