Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

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, 2016		December 31, 2015		December 31, 2014
Current:
Federal	$	999	$	1,211	$	1,190
State	127		168		169
Total current	1,126		1,379		1,359
Deferred:
Federal	901		1,097		852
State	97		51		89
Total deferred	998		1,148		941
Total	$	2,124	$	2,527	$	2,300

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, 2016		December 31, 2015		December 31, 2014
U.S. Federal statutory income tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	2.5		2.2		2.7
Other, net	(0.2	)	0.1		(0.4	)
Effective tax rate	37.3	%	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, 2016			December 31, 2015
Deferred tax liabilities:
Property and equipment	$	(20,634	)	$	(19,660	)
Other	(340		)	(341		)
Total deferred tax liabilities	(20,974		)	(20,001		)
Deferred tax assets:
Compensation and benefits	334			328
Casualty and environmental	278			293
Pension and retiree health and welfare benefits	89			126
Long-term debt fair value adjustment under acquisition method accounting	76			96
Intangible assets and liabilities	72			100
Other	259			231
Total deferred tax assets	1,108			1,174
Net deferred tax liability	$	(19,866	)	$	(18,827	)
Non-current deferred income tax liability	$	(19,866	)	$	(19,072	)
Current portion of deferred income taxes	—			245
Net deferred tax liability	$	(19,866	)	$	(18,827	)

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, 2016			December 31, 2015			December 31, 2014
Beginning balance	$	69		$	78		$	56
Additions for tax positions related to current year	4			7			16
Additions (reductions) for tax positions taken in prior years	(1		)	(8		)	13
Additions (reductions) for tax positions as a result of:
Settlements	1			1			(1		)
Lapse of statute of limitations	(11		)	(9		)	(6		)
Ending balance	$	62		$	69		$	78