Annual report pursuant to Section 13 and 15(d)

Benefit Costs Included in Accumulated Other Comprehensive Loss that have not yet Recognized in Net Periodic Pension Cost (Detail)

v2.4.0.6
Benefit Costs Included in Accumulated Other Comprehensive Loss that have not yet Recognized in Net Periodic Pension Cost (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]      
Accumulated other comprehensive loss $ 300.3 $ 241.3 $ 216.2
Pension Benefits
      
Defined Benefit Plan Disclosure [Line Items]      
Prior service cost, net of accumulated taxes of $0.9 and $1.3 in 2011 and 2010, respectively, for pension benefits and $(0.4) in 2011 and 2010 for other benefits 1.8 2.2  
Net actuarial loss, net of accumulated taxes of $165.6 and $130.6 in 2011 and 2010, respectively, for pension benefits and $6.0 and $7.1 in 2011 and 2010, respectively, for other benefits 288.6 227.5  
Accumulated other comprehensive loss 290.4 229.7  
Other Benefits
      
Defined Benefit Plan Disclosure [Line Items]      
Prior service cost, net of accumulated taxes of $0.9 and $1.3 in 2011 and 2010, respectively, for pension benefits and $(0.4) in 2011 and 2010 for other benefits (0.6) (0.8)  
Net actuarial loss, net of accumulated taxes of $165.6 and $130.6 in 2011 and 2010, respectively, for pension benefits and $6.0 and $7.1 in 2011 and 2010, respectively, for other benefits 10.5 12.4  
Accumulated other comprehensive loss $ 9.9 $ 11.6