Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Components of Tax Expense (Benefit) on Income from Continuing Operations

The components of the Corporation’s tax expense (benefit) on income from continuing operations are as follows:

years ended December 31 (add 000)	2016			2015			2014
Federal income taxes:
Current	$	97,975		$	20,627		$	35,313
Deferred		68,899			85,295			46,616
Total federal income taxes		166,874			105,922			81,929
State income taxes:
Current		15,189			18,153			10,307
Deferred		(1,149	)		930			3,376
Total state income taxes		14,040			19,083			13,683
Foreign income taxes:
Current		1,064			99			1,262
Deferred		(394	)		(241	)		(2,027	)
Total foreign income taxes		670			(142	)		(765	)
Total taxes on income	$	181,584		$	124,863		$	94,847

Summary of Effective Income Tax Rate on Continuing Operations

The Corporation’s effective income tax rate on continuing operations varied from the statutory United States income tax rate because of the following permanent tax differences:

years ended December 31	2016			2015			2014
Statutory tax rate		35.0	%		35.0	%		35.0	%
(Reduction) increase resulting from:
Effect of statutory depletion		(5.4	)		(7.8	)		(9.6	)
State income taxes, net of federal tax benefit		1.5			3.0			3.6
Domestic production deduction		(2.0	)		(0.1	)		(0.9	)
Transfer pricing		—			—			(0.2	)
Goodwill write off		—			0.4			3.9
Foreign tax rate differential		(0.1	)		—			1.3
Disallowed compensation		0.2			0.2			3.7
Transaction costs		0.1			—			2.4
Other items		0.6			(0.5	)		(1.1	)
Effective income tax rate		29.9	%		30.2	%		38.1	%

Components of Deferred Tax Assets and Liabilities

The principal components of the Corporation’s deferred tax assets and liabilities are as follows:

December 31	Deferred Assets (Liabilities)
(add 000)	2016			2015
Deferred tax assets related to:
Employee benefits	$	61,462		$	56,302
Inventories		71,490			75,907
Valuation and other reserves		38,206			42,857
Net operating loss carryforwards		10,507			11,448
Accumulated other comprehensive loss		82,793			67,757
AMT credit carryforward		2,771			48,197
Gross deferred tax assets		267,229			302,468
Valuation allowance on deferred tax assets		(8,521	)		(8,967	)
Total net deferred tax assets		258,708			293,501
Deferred tax liabilities related to:
Property, plant and equipment		(635,576	)		(593,767	)
Goodwill and other intangibles		(268,999	)		(266,436	)
Other items, net		(17,152	)		(16,757	)
Total deferred tax liabilities		(921,727	)		(876,960	)
Net deferred tax liability	$	(663,019	)	$	(583,459	)

Schedule of Unrecognized Tax Benefits Excluding Interest Correlative Effects

The following table summarizes the Corporation’s unrecognized tax benefits, excluding interest and correlative effects:

years ended December 31 (add 000)	2016			2015			2014
Unrecognized tax benefits at beginning of year	$	18,727		$	21,107		$	11,826
Gross increases – tax positions in prior years		2,401			3,079			2,075
Gross decreases – tax positions in prior years		(1,924	)		(3,512	)		(203	)
Gross increases – tax positions in current year		4,650			4,978			3,369
Gross decreases – tax positions in current year		(2,047	)		(594	)		(51	)
Lapse of statute of limitations		—			(6,331	)		(1,872	)
Unrecognized tax benefits assumed with acquisition		—			—			5,963
Unrecognized tax benefits at end of year	$	21,807		$	18,727		$	21,107