Income Taxes (Tables)

12 Months Ended

Dec. 31, 2012

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:

	2012			2011
	(in thousands)
Deferred income tax assets:
Allowance for doubtful accounts	$	305		$	288
Accrued expenses	6,655			6,513
Stock-based compensation	579			46
Insurance accruals	27,549			27,677
Unrealized loss on available-for-sale investments	449			1,078
Indirect tax benefits of unrecognized tax benefits	5,658			5,767
Other	1,011			1,230
Total gross deferred tax assets	42,206			42,599
Less valuation allowance	(449		)	(1,078		)
Net deferred tax assets	41,757			41,521
Deferred income tax liabilities:
Property and equipment	(77,177		)	(82,897		)
Goodwill	(1,351		)	(1,195		)
Prepaid expenses	(738		)	(689		)
	(79,266		)	(84,781		)
Net deferred tax liability	$	(37,509	)	$	(43,260	)

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, 2012 and 2011 as follows:

	2012			2011
	(in thousands)
Current assets, net	$	13,797		$	14,401
Noncurrent liabilities, net	(51,306		)	(57,661		)
	$	(37,509	)	$	(43,260	)

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

Income tax expense consists of the following:

	2012			2011			2010
	(in thousands)
Current income taxes:
Federal	$	38,148		$	20,460		$	40,165
State	1,636			2,195			(1,068		)
	39,784			22,655			39,097
Deferred income taxes:
Federal	(5,890		)	16,587			(7,804		)
State	140			(1,844		)	(636		)
	(5,750		)	14,743			(8,440		)
Total	$	34,034		$	37,398		$	30,657

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:

	2012			2011			2010
	(in thousands)
Federal tax at statutory rate (35%)	$	33,451		$	37,565		$	32,506
State taxes, net of federal benefit	1,554			981			(213		)
Non-taxable interest income	(48		)	(104		)	(243		)
Uncertain income tax penalties and interest, net	(616		)	(1,159		)	(1,377		)
Other	(307		)	115			(16		)
	$	34,034		$	37,398		$	30,657

Reconciliation of Unrecognized Tax Benefits [Table Text Block]

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

	2012			2011
	(in thousands)
Balance at January 1,	$	16,062		$	18,140
Additions based on tax positions related to current year	1,146			1,200
Additions for tax positions of prior years	1,075			—
Reductions for tax positions of prior years	(134		)	—
Reductions due to lapse of applicable statute of limitations	(2,426		)	(3,278		)
Settlements	—			—
Balance at December 31,	$	15,723		$	16,062