Weighted Average Pension Plan Assumptions (Detail) (Pension Benefits)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Benefits
Pension And Other Employee Benefit Plans [Line Items]
Benefit Obligations, Discount Rate	4.18%	5.09%
Benefit Obligations, Rate of Compensation Increase	4.40%	4.04%
Periodic Benefit Cost, Discount Rate	5.09%	5.77%	6.31%
Periodic Benefit Cost, Expected Long-Term Returns	7.20%	7.24%	7.24%
Periodic Benefit Cost, Rate of Compensation Increase	4.04%	4.00%	3.79%