Pension Plan Asset Allocations (Detail)	Dec. 31, 2012		Dec. 31, 2011
Defined Contribution Benefit Plans [Line Items]
Plan Assets	100.00%	[1]	100.00%	[1]
Equity Securities
Defined Contribution Benefit Plans [Line Items]
Plan Assets	74.00%		78.00%
Cash and Cash Equivalents
Defined Contribution Benefit Plans [Line Items]
Plan Assets	20.00%		15.00%
Debt Securities
Defined Contribution Benefit Plans [Line Items]
Plan Assets	6.00%		7.00%

[1] Our overall investment strategy is to achieve an asset allocation within the following ranges to achieve an appropriate rate of return relative to risk