Note 7 - Taxes on Income (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			34.00%	34.00%	34.00%
Income Tax Expense (Benefit)	$ 5,000		$ 9,760	$ 5,260	$ 5,830
Tax Adjustments, Settlements, and Unusual Provisions	4,000		4,000
Net Discrete Tax Adjustment, Tax Act			3,300
Net Discrete Tax Adjustment, Other Miscellaneous Discrete Items			700
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			$ 1,700
Accumulated Foreign Earnings and Profits Tax Rate, Liquid Assets			15.50%
Accumulated Foreign Earnings and Profits Tax Rate, Unremitted Foreign E&P			8.00%
Income Tax Expense (Benefit), Transition Tax, Net			$ 1,500
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			100	100	100
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations			100	100	$ 100
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	100		100	100
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	100		$ 100
Domestic Tax Authority [Member] | Earliest Tax Year [Member]
Open Tax Year			2015
State and Local Jurisdiction [Member] | Earliest Tax Year [Member]
Open Tax Year			2011
Other Noncurrent Liabilities [Member]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 500		$ 500	$ 500
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%