Note 7 - Taxes on Income - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory Federal income tax rate	34.00%	34.00%	34.00%
State and local income taxes, net of Federal income tax benefit	1.50%	1.90%	1.60%
Effect of change in unrecognized tax benefit			(0.10%)
Current year untaxed foreign income	(6.50%)	(5.10%)	(6.00%)
Foreign Taxes	1.40%
Non-deductible share-based employee compensation expense	1.10%	1.20%	1.30%
Excess tax benefit from stock compensation	(7.20%)	(4.40%)
Federal tax credits	(0.50%)	(0.80%)
Tax Cut and Jobs Act deferred tax re-measurement	6.90%
Tax on undistributed foreign earnings	2.90%
Transition tax (repatriation)	5.90%
Other items	(0.10%)	(0.40%)	0.10%
Effective income tax rate	39.40%	26.40%	30.90%