Note 7 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

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

	Years ended December 31,
	201 7			201 6		201 5
Current:
Federal	$	134,284		$	191,422	$	160,235
State and local		23,456			21,871		22,306
		157,740			213,293		182,541
Deferred:
Federal		(261,592	)		45,846		71,292
State and local		12,828			4,568		9,135
		(248,764	)		50,414		80,427
Tot al tax expense/(benefit)	$	(91,024	)	$	263,707	$	262,968

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

	Years ended December 31,
	201 7			201 6			201 5
Income tax at federal statutory rate	$	208,334		$	243,529		$	241,571
State tax, net of federal effect		18,334			19,165			18,671
Federal tax reform		(309,223	)		-			-
Benefit of stock compensation		(4,907	)		-			-
199/R&D credit		(7,056	)		-			-
Nondeductible meals and entertainment		1,374			1,419			1,420
Change in effective state tax rate, net of federal benefit		3,403			(1,055	)		1,761
Other, net		(1,283	)		649			(455	)
Total tax expense	$	(91,024	)	$	263,707		$	262,968

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

	December 31,
	201 7			201 6
Deferred tax assets:
Insurance accruals	$	27,700		$	34,788
Allowance for doubtful accounts		6,605			2,347
Compensation accrual		3,661			10,443
Deferred compensation accrual		17,620			26,062
Federal benefit of state uncertain tax positions		8,681			14,085
State NOL carry-forward		4,944			3,444
Other		3,134			3,853
Total gross deferred tax assets		72,345			95,022
Valuation allowance		(4,944	)		(3,444	)
Total deferred tax assets, net of valuation allowance		67,401			91,578
Deferred tax liabilities:
Plant and equipment, principally due to differences in depreciation		566,396			831,555
Prepaid permits and insurance, principally due to expensing for income tax purposes		28,089			37,119
Other		14,786			13,538
Total gross deferred tax liabilities		609,271			882,212
Net deferred tax liability	$	541,870		$	790,634

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

	December 31,
	201 7			201 6			201 5
Beginning balance	$	35.4		$	32.0		$	31.6
Additions based on tax positions related to the current year		11.6			10.3			9.4
Additions/(reductions) based on tax positions taken in prior years		5.4			(3.2	)		(2.5	)
Reductions due to settlements		(2.4	)		(0.4	)		(3.0	)
Reductions due to lapse of applicable statute of limitations		(4.7	)		(3.3	)		(3.5	)
Ending balance	$	45.3		$	35.4		$	32.0