Note 9 - Income Taxes - Reconciliation of the Federal Statutory Rate to Effective Tax Rate (Details)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Federal statutory rate	21.00%	21.00%	21.00%
State tax, net of federal benefit	2.20%	1.90%	1.40%
Effect of foreign taxes	1.10%	2.10%	3.80%
Federal tax on foreign income	0.40%	0.80%	1.40%
Valuation allowance	1.40%	0.60%	(3.20%)
Foreign deferred tax liability offset	(0.20%)	(0.40%)	(0.30%)
Manufacturing deduction	0.00%	0.00%	0.00%
Research & development tax credits	(0.60%)	(1.20%)	(0.70%)
Stock options	(2.30%)	(8.80%)	(3.30%)
Uncertain tax positions	0.30%	1.00%	0.80%
Other permanent differences	(0.60%)	0.50%	(0.70%)
Change in tax laws	0.00%	0.00%	0.00%
Deferred tax remeasurement	0.00%	0.00%	0.00%
Other	(0.30%)	(0.20%)	(0.90%)
Effective tax rate	22.40%	17.30%	19.30%

Effective income tax rate reconciliation deductible expense manufacturing deduction.

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Effective income tax rate reconciliation deferred tax remeasurement.

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Effective income tax rate reconciliation foreign deferred tax liability offset and adjustment.

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Effective income tax rate reconciliation other permanent differences.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax contingencies. Includes, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

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