Note 17 - Reconciliation Between U.S. Federal Statutory Rate and Effective Rate (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statutory federal income tax rate	35.00%	35.00%	35.00%
State tax expense, net of federal benefit	4.80%	4.90%	4.80%
Permanent items, including nondeductible expenses	(0.30%)	0.10%	(0.20%)
State investment tax credit	0.00%	(0.10%)	(0.10%)
Federal, state and foreign research and development credits	(0.40%)	(0.70%)	(0.50%)
Foreign rate differential	0.10%	0.20%	0.10%
Domestic production deduction	(2.90%)	(1.70%)	(2.40%)
Effective income tax rate	36.30%	37.70%	36.70%