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Weighted Average Assumptions Used to Determine Benefit Obligation (Detail)
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
PENSION BENEFIT PLANS
     
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 4.90% 5.70% 5.75%
Rate of salaried compensation increase   4.00% 4.00%
OTHER POSTRETIREMENT EMPLOYEE BENEFIT PLANS
     
Defined Benefit Plan Disclosure [Line Items]      
Discount rate 4.95% 5.60% 5.75%