Note 8 - Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statutory federal rate applied to income before income tax expense	$ 60,406	$ 67,647	$ 36,992
Current year permanent items	3,065	2,408	1,830
State and local taxes, net of federal tax benefit	14,004	7,889	5,056
Change in valuation allowance	(75)	(1,457)	(151)
Reserve for uncertain tax positions	(63)	757	(698)
Rate change due to enactment of tax reform		(145,997)	0
Other items, net	(490)	79	389
Income tax expense (benefit) as recorded	$ 76,847	$ (68,674)	$ 43,418
Effective income tax rate	26.70%	35.50%	41.10%