Weighted Average Asset Allocation for Funded Pension Benefit Plans (Detail) (Funded Defined Benefit Pension Plans)	Dec. 31, 2011	Dec. 31, 2010
Funded Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Equity securities	62.30%	62.70%
Fixed income securities	36.50%	36.20%
Cash equivalents	1.20%	1.10%
Defined Benefit Plan, Actual Plan Asset Allocations, Total	100.00%	100.00%