Note 6 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2013

Income Tax Disclosure [Abstract]

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

	Years ended December 31,
	2013		2012		2011
Current:
Federal	$	144,299	$	152,140	$	32,845
State and local		18,811		21,095		8,171
		163,110		173,235		41,016
Deferred:
Federal		41,811		12,458		110,495
State and local		6,265		8,594		7,216
		48,076		21,052		117,711
Total tax expense	$	211,186	$	194,287	$	158,727

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

	Years ended December 31,
	2013			2012			2011
Income tax at federal statutory rate	$	193,749		$	176,624		$	145,506
State tax, net of federal effect		13,551			16,191			9,668
Nondeductible meals and entertainment		1,543			1,568			1,570
Change in effective state tax rate, net of federal benefit		3,708			126			1,611
Change in valuation allowance		(755	)		-			552
Other, net		(610	)		(222	)		(180	)
Total tax expense	$	211,186		$	194,287		$	158,727

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

	December 31,
	2013			2012
Deferred tax assets:
Insurance accruals	$	14,938		$	9,713
Allowance for doubtful accounts		2,077			1,715
Compensation accrual		13,783			16,851
Deferred compensation accrual		25,398			25,997
Federal benefit of state uncertain tax positions		12,099			10,586
Capital loss carry-forward		1,443			2,197
Other		3,586			3,403
Total gross deferred tax assets		73,324			70,462
Valuation allowance		(1,994	)		(2,749	)
Total deferred tax assets, net of valuation allowance		71,330			67,713
Deferred tax liabilities:
Plant and equipment, principally due to differences in depreciation		615,811			571,830
Prepaid permits and insurance, principally due to expensing for income tax purposes		24,554			19,069
Other		11,415			9,188
Total gross deferred tax liabilities		651,780			600,087
Net deferred tax liability	$	580,450		$	532,374

Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]

	December 31,
	2013			2012			2011
Beginning balance	$	25.8		$	17.4		$	17.3
Additions based on tax positions related to the current year		7.0			7.1			4.0
Additions/(reductions) based on tax positions taken in prior years		(1.2	)		4.2			(0.3	)
Reductions due to settlements		(0.1	)		-			(0.4	)
Reductions due to lapse of applicable statute of limitations		(1.8	)		(2.9	)		(3.2	)
Ending balance	$	29.7		$	25.8		$	17.4