Schedule of Plan Assets Category (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Total	100.00%	100.00%
Equity Securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Asset Allocation	47.00%	45.00%
Fixed income securities
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Asset Allocation	49.00%	50.00%
Other
Fair Value Hierarchy Of Plan Assets By Category [Line Items]
Asset Allocation	4.00%	5.00%