Note 6 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Member]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 400	$ 200
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 1,300	$ 1,300
Effective Income Tax Rate Reconciliation, Percent	38.40%	47.00%	39.00%
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	$ 4,300
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	1,569	$ 1,795	$ 5,233
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	400	$ 200
Decrease in Unrecognized Tax Benefits is Reasonably Possible	800
Operating Loss Carryforwards	$ 1,300