Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Tax Disclosure [Abstract]

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

Deferred tax assets and liabilities as of December 31 are as follows:

	2014			2013
	(in thousands)
Deferred income tax assets:
Allowance for doubtful accounts	$	478		$	291
Accrued expenses	8,969			6,980
Stock-based compensation	677			648
Insurance accruals	25,395			26,000
State net operating loss carryforward	3,241			682
Indirect tax benefits of unrecognized tax benefits	4,595			4,846
Other	772			1,207
Total gross deferred tax assets	44,127			40,654
Less valuation allowance	—			—
Net deferred tax assets	44,127			40,654
Deferred income tax liabilities:
Property and equipment	(125,611		)	(85,849		)
Goodwill	(2,385		)	(1,835		)
Prepaid expenses	(2,969		)	(741		)
	(130,965		)	(88,425		)
Net deferred tax liability	$	(86,838	)	$	(47,771	)

Summary of Deferred Tax Assets (Liabilities) by Balance Sheet Classification [Table Text Block]

The deferred tax amounts above have been classified in the accompanying consolidated balance sheets at December 31, 2014 and 2013 as follows:

	2014			2013
	(in thousands)
Current assets, net	$	14,767		$	14,177
Long-term liabilities, net	(101,605		)	(61,948		)
	$	(86,838	)	$	(47,771	)

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

Income tax expense consists of the following:

	2014		2013		2012
	(in thousands)
Current income taxes:
Federal	$	6,860	$	30,560	38,148
State	855		1,152		1,636
	7,715		31,712		39,784
Deferred income taxes:
Federal	36,706		7,192		(5,890		)
State	2,362		3,070		140
	39,068		10,262		(5,750		)
Total	$	46,783	$	41,974	$	34,034

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The income tax provision differs from the amount determined by applying the U.S. federal tax rate as follows:

	2014			2013			2012
	(in thousands)
Federal tax at statutory rate (35%)	$	46,066		$	39,395		33,451
State taxes, net of federal benefit	2,737			3,242			1,554
Non-taxable interest income	(7		)	(20		)	(48		)
Uncertain income tax penalties and interest, net	(993		)	(766		)	(616		)
Other	(1,020		)	123			(307		)
	$	46,783		$	41,974		$	34,034

Reconciliation of Unrecognized Tax Benefits [Table Text Block]

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

	2014			2013
	(in thousands)
Balance at January 1,	$	13,432		$	15,723
Additions based on tax positions related to current year	983			843
Additions for tax positions of prior years	277			616
Reductions for tax positions of prior years	—			(300		)
Reductions due to lapse of applicable statute of limitations	(2,060		)	(1,984		)
Settlements	—			(1,466		)
Balance at December 31,	$	12,632		$	13,432