Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Schedule of income tax provision for continuing operations

The income tax provision for continuing operations consisted of the following for the years ended December 31:

In millions	2016			2015			2014
Current:
Federal	$	2,803		$	3,065		$	2,581
State	511			555			495
	3,314			3,620			3,076
Deferred:
Federal	5			(180		)	(43		)
State	(2		)	(54		)	—
	3			(234		)	(43		)
Total	$	3,317		$	3,386		$	3,033

Reconciliation of the statutory income tax rate to the Company's effective income tax rate for continuing operations

The following table is a reconciliation of the statutory income tax rate to the Company’s effective income tax rate for continuing operations for the years ended December 31:

	2016		2015		2014
Statutory income tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	4.1		4.0		4.3
Other	(0.7	)	0.3		0.2
Effective income tax rate	38.4	%	39.3	%	39.5	%

Summary of the significant components of the Company's deferred tax assets and liabilities

The following table is a summary of the components of the Company’s deferred tax assets and liabilities as of December 31:

In millions	2016			2015
Deferred tax assets:
Lease and rents	$	375		$	378
Inventory	57			99
Employee benefits	400			359
Allowance for doubtful accounts	301			279
Retirement benefits	65			105
Net operating loss and capital loss carryforwards	125			115
Deferred income	144			83
Other	336			498
Valuation allowance	(135		)	(115		)
Total deferred tax assets	1,668			1,801
Deferred tax liabilities:
Depreciation and amortization	(5,882		)	(6,018		)
Total deferred tax liabilities	(5,882		)	(6,018		)
Net deferred tax liabilities	$	(4,214	)	$	(4,217	)

Reconciliation of the beginning and ending amount of unrecognized tax benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:

In millions	2016			2015			2014
Beginning balance	$	338		$	188		$	117
Additions based on tax positions related to the current year	68			57			32
Additions based on tax positions related to prior years	70			122			70
Reductions for tax positions of prior years	(100		)	(11		)	(15		)
Expiration of statutes of limitation	(22		)	(13		)	(15		)
Settlements	(47		)	(5		)	(1		)
Ending balance	$	307		$	338		$	188