Weighted Average Asset Allocation for Company's Funded Pension Benefit Plans (Detail) (Funded Defined Benefit Pension Plans)	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	62.90%	62.30%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	36.10%	36.50%
Cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocation	1.00%	1.20%