Income Taxes (Tables)

12 Months Ended

Dec. 31, 2012

Income Taxes [Abstract]

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

Income tax expense was as follows (in millions):

	Successor						Predecessor
	Year Ended		Year Ended		February 13 – December 31, 2010		January 1 – February 12, 2010
	December 31, 2012		December 31, 2011
Current:
Federal	$	1,204	$	220	$	593	$	23
State	141		40		73		3
Total current	1,345		260		666		26
Deferred:
Federal	591		1,375		626		113
State	69		134		84		14
Total deferred	660		1,509		710		127
Total	$	2,005	$	1,769	$	1,376	$	153

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

Reconciliation of the U.S. federal statutory income tax rate to the effective tax rate was as follows:

	Successor						Predecessor
	Year Ended		Year Ended		February 13 – December 31, 2010		January 1 – February 12, 2010
	December 31, 2012		December 31, 2011
U.S. Federal statutory income tax rate	35.0	%	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	2.5		2.4		3.1		3.1
Tax law change (Medicare Part D)	—		—		0.5		—
Other, net	(0.2	)	(0.1	)	(0.5	)	2.5
Effective tax rate	37.3	%	37.3	%	38.1	%	40.6	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

The components of deferred tax assets and liabilities were as follows (in millions):

	Successor
	December 31, 2012			December 31, 2011
Deferred tax liabilities:
Property and equipment	$	(17,330	)	$	(16,864	)
Hedging	(10		)	(18		)
Other	(336		)	(304		)
Total deferred tax liabilities	(17,676		)	(17,186		)
Deferred tax assets:
Intangible assets and liabilities	275			372
Casualty and environmental	303			370
Compensation and benefits	358			374
Long-term debt fair value adjustment under acquisition method accounting	173			209
Pension and retiree health and welfare benefits	332			305
Other	257			214
Total deferred tax assets	1,698			1,844
Net deferred tax liability	$	(15,978	)	$	(15,342	)
Non-current deferred income tax liability	$	(16,319	)	$	(15,637	)
Current portion of deferred income taxes	341			295
Net deferred tax liability	$	(15,978	)	$	(15,342	)

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in millions):

	Successor									Predecessor
	Year Ended			Year Ended			February 13 – December 31, 2010			January 1  –  February 12, 2010
	December 31, 2012			December 31, 2011
Beginning balance	$	110		$	112		$	167		$	166
Additions for tax positions related to current year	12			47			24			1
Reductions for tax positions taken in prior years	(2		)	(40		)	(58		)	—
(Reductions) additions for tax positions as a result of:
Settlements	(53		)	8			(10		)	—
Lapse of statute of limitations	(19		)	(17		)	(11		)	—
Ending balance	$	48		$	110		$	112		$	167