Note 7 - Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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/(benefit)	$ (91,024)	$ 263,707	$ 262,968

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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