Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Income Taxes (Textual)
Cyren Ltd. Corporate tax rate	23.00%	23.00%
Cyren Ltd. Net operating loss carrforwards	$ 91,682
Cyren Ltd. Capital loss carryforwards	17,846
Increases Valuation Allowance [Member]
Income Taxes (Textual)
Increase in valuation allowance amount	1,096	$ 3,754
Internal Revenue Service I R S [Member]
Income Taxes (Textual)
Cyren Inc. Federal tax purposes	39,720
Cyren Inc. State tax purposes	$ 11,090
Cyren Inc. carryforward losses description	Expire in the years 2020 through 2039.
Foreign Tax Authority [Member]
Income Taxes (Textual)
Cyren GmbH Corporate tax rate	30.00%

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

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

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Amount 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 state and local income tax settlement.

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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The aggregate cost of investments for Federal income tax purposes.

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The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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A description of the origin, nature, and characteristics of the tax credit carryforward.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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