Income Taxes Components of Deferred Tax Assets / (Liabilities) (Details) (Successor [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Successor [Member]
Components of Deferred Tax Assets and Liabilities [Line Items]
Deferred Tax Liabilities, Property, Plant and Equipment	$ (17,330)	$ (16,864)
Deferred Tax Liabilities, Hedging	(10)	(18)
Deferred Tax Liabilities, Other	(336)	(304)
Deferred Tax Liabilities, Gross	(17,676)	(17,186)
Deferred Tax Asset, Tax Deferred Expense, Intangible Assets and Liabilities	275	372
Deferred Tax Assets, Tax Deferred Expense, Casualty and environmental	303	370
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits	358	374
Deferred Tax Assets, Tax Deferred Expense, Long-term Debt Fair Value Adjustment	173	209
Deferred Tax Asset, Deferred Tax Expense, Pension and Retiree Health and Welfare Benefits	332	305
Deferred Tax Assets, Other	257	214
Deferred Tax Assets, Gross	1,698	1,844
Deferred Tax Liabilities, Net	(15,978)	(15,342)
Deferred Tax Liabilities, Net, Noncurrent	(16,319)	(15,637)
Deferred Tax Assets, Net, Current	$ 341	$ 295