Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Taxes [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

Income tax expense (benefit) was as follows (in millions):

	Years ended December 31,
	2023		2022		2021
Current:
Federal	$	1,193	$	1,468	$	1,173
State	235		284		252
Total current	1,428		1,752		1,425
Deferred:
Federal	174		88		422
State	(75)		(78)		24
Total deferred	99		10		446
Total	$	1,527	$	1,762	$	1,871

Schedule of Effective Income Tax Rate Reconciliation

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

	Years ended December 31,
	2023		2022		2021
U.S. Federal statutory income tax rate	21.0	%	21.0	%	21.0	%
State income taxes, net of federal tax benefit	1.9		1.9		2.8
Other, net	0.2		—		—
Effective tax rate	23.1	%	22.9	%	23.8	%

Schedule of Deferred Tax Assets and Liabilities

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

	December 31, 2023		December 31, 2022
Deferred tax liabilities:
Property and equipment	$	(14,989)	$	(14,895)
Operating lease right-of-use assets	(203)		(233)
Other	(682)		(634)
Total deferred tax liabilities	(15,874)		(15,762)
Deferred tax assets:
Operating lease liabilities	201		232
Compensation and benefits	173		166
Casualty and environmental	102		97
Other	176		157
Total deferred tax assets	652		652
Net deferred tax liability	$	(15,222)	$	(15,110)

Schedule of Unrecognized Tax Benefits Roll Forward

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

	Years ended December 31,
	2023		2022		2021
Beginning balance	$	52	$	46	$	41
Additions for tax positions related to current year	6		11		9
Additions (reductions) for tax positions taken in prior years	(2)		—		—
Additions (reductions) for tax positions as a result of:
Lapse of statute of limitations	(9)		(5)		(4)
Ending balance	$	47	$	52	$	46