Represents stock rotation reserve.

No definition available.

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- Definition

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

+ References

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

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- Definition

Sum of the carrying amounts as of the balance sheet date of deferred costs capitalized at the end of the reporting period that are expected to be charged against earnings within one year or the normal operating cycle, if longer.

+ References

+ Details

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- Definition

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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Balance Type:	na
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- Definition

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
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- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

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Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2018	Jan. 01, 2017
Allowance for Doubtful Accounts Receivable, Current	$ 0	$ 0
Foreign Currency Transaction Gain (Loss), before Tax	(550)	65	$ 608
Available-for-sale Securities	229,221	185,831
Goodwill, Impairment Loss	0	0	$ 0
Stock Rotation Reserve	2,647	1,937
Cumulative Effect of New Accounting Principle in Period of Adoption
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	(5,141)
Accounting Standards Update 2016-09 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 5,100
Accounting Standards Update 2014-09 [Member] \| Retained Earnings [Member] \| Scenario, Forecast [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 800
Distributors with Price Adjustment Rights [Member]
Deferred Revenue	1,900	3,700
Deferred Costs, Current	$ 200	$ 300
Sales Revenue, Goods, Net [Member] \| Customer Concentration Risk [Member] \| Distributor Sales [Member]
Concentration Risk, Percentage	88.00%	88.00%	88.00%
Land Use Rights [Member]
Finite-Lived Intangible Asset, Useful Life	50 years
Minimum [Member] \| Know-How And Developed Technologies [Member]
Finite-Lived Intangible Asset, Useful Life	3 years
Maximum [Member] \| Know-How And Developed Technologies [Member]
Finite-Lived Intangible Asset, Useful Life	5 years
Building and Building Improvements [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life	20 years
Building and Building Improvements [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life	40 years
Computer Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Computer Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life	7 years
Transportation Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life	5 years
Transportation Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life	15 years
Furniture and Fixtures [Member] \| Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Furniture and Fixtures [Member] \| Maximum [Member]
Property, Plant and Equipment, Useful Life	5 years
Auction Rate Securities [Member]
Available-for-sale Securities	$ 5,300	$ 5,400
Interest and Other Income [Member]
Foreign Currency Transaction Gain (Loss), before Tax	$ (600)	$ 100	$ 600