Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Components of Income Tax (Benefit) Expense

The components of the Company’s income tax (benefit) expense are as follows:

years ended December 31 (add 000)	2017			2016			2015
Federal income taxes:
Current	$	129,236		$	97,975		$	20,627
Deferred		(239,304	)		68,899			85,295
Total federal income tax (benefit) expense		(110,068	)		166,874			105,922
State income taxes:
Current		14,843			15,189			18,153
Deferred		(882	)		(1,149	)		930
Total state income taxes		13,961			14,040			19,083
Foreign income taxes:
Current		1,175			1,064			99
Deferred		475			(394	)		(241	)
Total foreign income taxes		1,650			670			(142	)
Income tax (benefit) expense	$	(94,457	)	$	181,584		$	124,863

Summary of Effective Income Tax Rate

The Company’s effective income tax rate varied from the statutory United States income tax rate because of the following tax differences:

years ended December 31	2017			2016			2015
Statutory tax rate		35.0	%		35.0	%		35.0	%
(Reduction) increase resulting from:
Provisional remeasurement of deferred taxes due to 2017 Tax Act		(41.7	)		—			—
Effect of statutory depletion		(5.6	)		(5.4	)		(7.8	)
State income taxes, net of federal tax benefit		1.5			1.5			3.0
Domestic production deduction		(2.2	)		(2.0	)		(0.1	)
Stock based compensation		(1.0	)		(0.1	)		(0.3	)
Other items		(1.3	)		0.9			0.4
Effective income tax rate	(15.3%)				29.9	%		30.2	%

Components of Deferred Tax Assets and Liabilities

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

December 31	Deferred Assets (Liabilities)
(add 000)	2017			2016
Deferred tax assets related to:
Employee benefits	$	16,059		$	61,462
Inventories		56,242			71,490
Valuation and other reserves		22,989			38,206
Net operating loss carryforwards		11,780			10,507
Accumulated other comprehensive loss		80,116			82,793
AMT credit carryforward		-			2,771
Gross deferred tax assets		187,186			267,229
Valuation allowance on deferred tax assets		(10,349	)		(8,521	)
Total net deferred tax assets		176,837			258,708
Deferred tax liabilities related to:
Property, plant and equipment		(407,400	)		(635,576	)
Goodwill and other intangibles		(168,506	)		(268,999	)
Other items, net		(11,654	)		(17,152	)
Total deferred tax liabilities		(587,560	)		(921,727	)
Deferred income taxes, net	$	(410,723	)	$	(663,019	)

Schedule of Unrecognized Tax Benefits Excluding Interest Correlative Effects

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

years ended December 31 (add 000)	2017			2016			2015
Unrecognized tax benefits at beginning of year	$	21,807		$	18,727		$	21,107
Gross increases – tax positions in prior years		1,396			2,401			3,079
Gross decreases – tax positions in prior years		(672	)		(1,924	)		(3,512	)
Gross increases – tax positions in current year		4,961			4,650			4,978
Gross decreases – tax positions in current year		(946	)		(2,047	)		(594	)
Lapse of statute of limitations		(4,179	)		-			(6,331	)
Unrecognized tax benefits at end of year	$	22,367		$	21,807		$	18,727