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Income Taxes - Summary of Deferred Tax Assets and Liabilities (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Income Taxes [Line Items]    
Tax benefit of loss carryforwards $ 628 $ 527
Liabilities currently not deductible for tax 263 219
Tax credit carryforwards 35 73
Unrealized loss on cash flow hedges and retirement liabilities 48 51
Deferred tax assets, Gross, Total 974 870
Valuation allowance against tax benefit of loss carryforwards (504) (454)
Other valuation allowance (45) (103)
Deferred Tax Assets, Net, Total 425 313
Tax depreciation in excess of book depreciation 199 135
Other assets book value in excess of tax value 77 20
Unrealized gain on cash flow hedges and retirement liabilities 19 8
Other 30 0
Deferred tax liabilities, total 325 163
Net deferred tax assets $ 100 $ 150