Income Taxes - Additional Information (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
Income Tax Contingency [Line Items]
Effective tax rate	33.60%	27.80%	32.90%	30.40%
Overall increase (decrease) in unrecognized tax benefits (UTPs)			$ (73.9)	$ 6.4
Gross
Income Tax Contingency [Line Items]
Overall increase (decrease) in unrecognized tax benefits (UTPs)	7.6		(75.4)
Net
Income Tax Contingency [Line Items]
Overall increase (decrease) in unrecognized tax benefits (UTPs)	5.2		$ (45.5)