Income Taxes (Tables)

12 Months Ended

Dec. 31, 2013

Income Taxes [Abstract]

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

Income tax expense was as follows (in millions):

	Year Ended			Year Ended		Year Ended
	December 31, 2013			December 31, 2012		December 31, 2011
Current:
Federal	$	1,346		$	1,204	$	220
State	206			141		40
Total current	1,552			1,345		260
Deferred:
Federal	609			591		1,375
State	(26		)	69		134
Total deferred	583			660		1,509
Total	$	2,135		$	2,005	$	1,769

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:

	Year Ended		Year Ended		Year Ended
	December 31, 2013		December 31, 2012		December 31, 2011
U.S. Federal statutory income tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	2.0		2.5		2.4
Other, net	(1.0	)	(0.2	)	(0.1	)
Effective tax rate	36.0	%	37.3	%	37.3	%

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

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

	December 31, 2013			December 31, 2012
Deferred tax liabilities:
Property and equipment	$	(17,727	)	$	(17,330	)
Hedging	(11		)	(10		)
Pension and retiree health and welfare benefits	(13		)	—
Other	(347		)	(336		)
Total deferred tax liabilities	(18,098		)	(17,676		)
Deferred tax assets:
Compensation and benefits	371			358
Casualty and environmental	273			303
Intangible assets and liabilities	190			275
Long-term debt fair value adjustment under acquisition method accounting	141			173
Pension and retiree health and welfare benefits	—			332
Other	257			257
Total deferred tax assets	1,232			1,698
Net deferred tax liability	$	(16,866	)	$	(15,978	)
Non-current deferred income tax liability	$	(17,224	)	$	(16,319	)
Current portion of deferred income taxes	358			341
Net deferred tax liability	$	(16,866	)	$	(15,978	)

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):

	Year Ended			Year Ended			Year Ended
	December 31, 2013			December 31, 2012			December 31, 2011
Beginning balance	$	48		$	110		$	112
Additions for tax positions related to current year	16			12			47
Additions (reductions) for tax positions taken in prior years	1			(2		)	(40		)
Additions (reductions) for tax positions as a result of:
Settlements	1			(53		)	8
Lapse of statute of limitations	(10		)	(19		)	(17		)
Ending balance	$	56		$	48		$	110