Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional information (Detail)

Income Taxes - Additional information (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Income Taxes [Line Items]    
Effective income tax rate 22.20% 22.90%
Tax settlements of prior years tax audits $ 8.0  
Reductions due to settlement of foreign tax claim 3.5  
Tax benefits from partial release of a valuation allowance related to capital loss carryforwards 11.1  
Realization of unrecognized tax benefits   12.8
Decrease in unrecognized tax benefits and associated interest primarily due to the audit settlements 8.0  
Total unrecognized tax benefits 94.7  
Unrecognized tax benefits and interest 5.3  
Possible decrease in unrecognized income tax benefits $ 5.5