Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015		December 31, 2014		December 31, 2013
Current:
Federal	$	1,211	$	1,190	$	1,346
State	168		169		206
Total current	1,379		1,359		1,552
Deferred:
Federal	1,097		852		609
State	51		89		(26		)
Total deferred	1,148		941		583
Total	$	2,527	$	2,300	$	2,135

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, 2015		December 31, 2014		December 31, 2013
U.S. Federal statutory income tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	2.2		2.7		2.0
Other, net	0.1		(0.4	)	(1.0	)
Effective tax rate	37.3	%	37.3	%	36.0	%

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, 2015			December 31, 2014
Deferred tax liabilities:
Property and equipment	$	(19,660	)	$	(18,624	)
Other	(341		)	(363		)
Total deferred tax liabilities	(20,001		)	(18,987		)
Deferred tax assets:
Compensation and benefits	328			335
Casualty and environmental	293			307
Pension and retiree health and welfare benefits	126			202
Intangible assets and liabilities	100			132
Long-term debt fair value adjustment under acquisition method accounting	96			117
Other	231			248
Total deferred tax assets	1,174			1,341
Net deferred tax liability	$	(18,827	)	$	(17,646	)
Non-current deferred income tax liability	$	(19,072	)	$	(18,001	)
Current portion of deferred income taxes	245			355
Net deferred tax liability	$	(18,827	)	$	(17,646	)

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, 2015			December 31, 2014			December 31, 2013
Beginning balance	$	78		$	56		$	48
Additions for tax positions related to current year	7			16			16
Additions (reductions) for tax positions taken in prior years	(8		)	13			1
Additions (reductions) for tax positions as a result of:
Settlements	1			(1		)	1
Lapse of statute of limitations	(9		)	(6		)	(10		)
Ending balance	$	69		$	78		$	56