Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Summary of Deferred Tax Liabilities and Assets

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Deferred tax liabilities (assets) are comprised of the following at December 31 (in thousands):

	2017			2016
Depreciation	$	86,506		$	117,625
Other		93			1,414
Gross deferred tax liabilities		86,599			119,039
Allowance for doubtful accounts		(988	)		(1,225	)
Equity-based compensation		(2,607	)		(4,538	)
Employee benefits		(5,458	)		(6,115	)
Claims and insurance		(16,929	)		(23,241	)
Other		(1,194	)		(3,721	)
Gross deferred tax assets		(27,176	)		(38,840	)
Net deferred tax liability	$	59,423		$	80,199

Summary of Income Tax Provision (Benefit)

The income tax provision (benefit) for continuing operations consists of the following (in thousands):

	2017			2016		2015
Current:
U.S. federal	$	17,637		$	12,127	$	20,768
State		1,761			1,988		1,759
Total current income tax provision		19,398			14,115		22,527
Deferred:
U.S. federal		(21,221	)		12,599		8,570
State		445			181		(150	)
Total deferred income tax provision		(20,776	)		12,780		8,420
Total income tax provision	$	(1,378	)	$	26,895	$	30,947

Summary of Reconciliation Between Income Taxes and Effective Income Tax Provision

A reconciliation between income taxes at the federal statutory rate (35 percent) and the effective income tax provision is as follows (in thousands):

	2017			2016			2015
Provision at federal statutory rate		31,422		$	26,222		$	30,087
State income taxes, net		2,545			2,418			2,229
Tax Cuts and Jobs Act benefit		(33,910	)		—			—
Nondeductible business expenses (benefits)		(913	)		462			696
Tax credits		(190	)		(1,278	)		(1,532	)
Other, net		(332	)		(929	)		(533	)
Total provision	$	(1,378	)	$	26,895		$	30,947

Summary of Gross Unrecognized Tax Benefits

A reconciliation of the beginning and ending total amounts of gross unrecognized tax benefits is as follows (in thousands):

	2017			2016
Gross unrecognized tax benefits at beginning of year	$	1,280		$	1,158
Gross decreases in tax positions for prior years		(7	)		—
Gross increases in tax positions for current year		171			490
Settlements		—			(100	)
Lapse of statute of limitations		(351	)		(268	)
Gross unrecognized tax benefits at end of year	$	1,093		$	1,280