Weighted Average Assumptions For Post-Retirement Benefit Plans Other Than Pensions (Detail) (Other Benefits)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Benefits
Pension And Other Employee Benefit Plans [Line Items]
Benefit Obligations, Discount Rate	4.18%	5.09%
Benefit Obligations, Rate of Compensation Increase	3.50%	3.50%
Periodic Benefit Cost, Discount Rate	5.09%	5.77%	6.60%
Periodic Benefit Cost, Rate of Compensation Increase	3.50%	4.50%	4.50%