Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

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, 2014		December 31, 2013			December 31, 2012
Current:
Federal	$	1,190	$	1,346		$	1,204
State	169		206			141
Total current	1,359		1,552			1,345
Deferred:
Federal	852		609			591
State	89		(26		)	69
Total deferred	941		583			660
Total	$	2,300	$	2,135		$	2,005

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, 2014		December 31, 2013		December 31, 2012
U.S. Federal statutory income tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	2.7		2.0		2.5
Other, net	(0.4	)	(1.0	)	(0.2	)
Effective tax rate	37.3	%	36.0	%	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, 2014			December 31, 2013
Deferred tax liabilities:
Property and equipment	$	(18,624	)	$	(17,727	)
Hedging	(10		)	(11		)
Pension and retiree health and welfare benefits	—			(13		)
Other	(353		)	(347		)
Total deferred tax liabilities	(18,987		)	(18,098		)
Deferred tax assets:
Compensation and benefits	335			371
Casualty and environmental	307			273
Intangible assets and liabilities	132			190
Long-term debt fair value adjustment under acquisition method accounting	117			141
Pension and retiree health and welfare benefits	202			—
Other	248			257
Total deferred tax assets	1,341			1,232
Net deferred tax liability	$	(17,646	)	$	(16,866	)
Non-current deferred income tax liability	$	(18,001	)	$	(17,224	)
Current portion of deferred income taxes	355			358
Net deferred tax liability	$	(17,646	)	$	(16,866	)

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, 2014			December 31, 2013			December 31, 2012
Beginning balance	$	56		$	48		$	110
Additions for tax positions related to current year	16			16			12
Additions (reductions) for tax positions taken in prior years	13			1			(2		)
Additions (reductions) for tax positions as a result of:
Settlements	(1		)	1			(53		)
Lapse of statute of limitations	(6		)	(10		)	(19		)
Ending balance	$	78		$	56		$	48