Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

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	2015			2014			2013
Current:
Federal	$	3,065		$	2,581		$	2,623
State	555			495			437
	3,620			3,076			3,060
Deferred:
Federal	(180		)	(43		)	(115		)
State	(54		)	—			(17		)
	(234		)	(43		)	(132		)
Total	$	3,386		$	3,033		$	2,928

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:

	2015		2014		2013
Statutory income tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal tax benefit	4.0		4.3		4.0
Other	0.3		0.2		(0.1	)
Effective income tax rate	39.3	%	39.5	%	38.9	%

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

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

In millions	2015			2014
Deferred tax assets:
Lease and rents	$	378		$	396
Inventory	99			—
Employee benefits	359			311
Allowance for doubtful accounts	279			164
Retirement benefits	105			80
Net operating loss and capital loss carryforwards	115			74
Deferred income	83			261
Other	498			297
Valuation allowance	(115		)	(5		)
Total deferred tax assets	1,801			1,578
Deferred tax liabilities:
Inventories	—			(18		)
Depreciation and amortization	(6,018		)	(4,572		)
Total deferred tax liabilities	(6,018		)	(4,590		)
Net deferred tax liabilities	$	(4,217	)	$	(3,012	)

Schedule of net deferred tax assets (liabilities)

Net deferred tax assets (liabilities) are presented on the consolidated balance sheets as follows:

In millions	2015			2014
Deferred tax assets—current	$	1,220		$	985
Deferred tax assets—noncurrent (included in other assets)	—			39
Deferred tax liabilities—noncurrent	(5,437		)	(4,036		)
Net deferred tax liabilities	$	(4,217	)	$	(3,012	)

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	2015			2014			2013
Beginning balance	$	188		$	117		$	80
Additions based on tax positions related to the current year	57			32			19
Additions based on tax positions related to prior years	122			70			37
Reductions for tax positions of prior years	(11		)	(15		)	(1		)
Expiration of statutes of limitation	(13		)	(15		)	(17		)
Settlements	(5		)	(1		)	(1		)
Ending balance	$	338		$	188		$	117