Asset Allocations by Asset Category (Detail)	Dec. 31, 2012	Dec. 31, 2011
Domestic Plan
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations, by asset category	100.00%	100.00%
Domestic Plan | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations, by asset category	85.00%	85.00%
Domestic Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations, by asset category	15.00%	15.00%
TCN Plan
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations, by asset category	100.00%	100.00%
TCN Plan | Fixed Income
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations, by asset category	30.00%	30.00%
TCN Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Weighted average asset allocations, by asset category	70.00%	70.00%