Shareholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended			6 Months Ended
	Jun. 11, 2020	Nov. 07, 2019	Dec. 05, 2018	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Shareholders' Equity (Textual)
Options grant/vest, description							The options vest and become exercisable at a rate of 1/16 of the options every three months.
Conversion price, per share		$ 3.73
Gross proceeds		$ 8,019
Maturity date							Mar. 19, 2024
Interest expense							$ 283	$ 282
Convertible Notes Payable [Member]
Shareholders' Equity (Textual)
Aggregate principal amount			$ 10,000		$ 1,000
Interest rate			5.75%
Debt instrument, description			(i) 50% cash and (ii) 50% cash or ordinary shares at Cyren's election.
Notes, term			3 years
Conversion price, per share			$ 3.90
Maturity date			Dec. 31, 2021
Issuance expenses					800
Convertible Debentures [Member]
Shareholders' Equity (Textual)
Aggregate principal amount					$ 9,400
Interest rate							5.75%
Debt instrument, description	One of the debenture holders converted $48 of principal plus interest of their debentures.
Notes, term							4 years
Convertible shares	64,542						1,333
Conversion price, per share				$ 0.75			$ 0.75
Maturity date							Mar. 31, 2024
Interest expense				$ 187		$ 211	$ 44	$ 49
Accrued interest							163
Amortization debt issuance costs							$ 5
Non-Employee Plan [Member]
Shareholders' Equity (Textual)
Options vesting period							4 years
Options expiration term, description							Options granted under the Non-Employee Director Plan generally expire after six years from the date of grant.
Annual meeting, description							On July 30, 2019 the shareholders of the Company approved an increase in the number of Ordinary Shares reserved for issuance under the Non-Employee Director Plan and its respective Israeli Appendix to a total of 1,150,000 Ordinary Shares.
Non Vested Stock Options [Member] | Non-Employee Plan [Member]
Shareholders' Equity (Textual)
Ordinary shares available for future grant				842,882			842,882
Unrecognized compensation expense				$ 2,046			$ 2,046
Recognized over remaining weighted average period							2 years 7 months 10 days
Restricted Stock Units (RSUs) [Member]
Shareholders' Equity (Textual)
Unrecognized compensation expense				$ 2,087			$ 2,087
Recognized over remaining weighted average period							2 years 6 months 10 days
Stock Compensation Plan [Member]
Shareholders' Equity (Textual)
Options grant/vest, description							The per share exercise price for options shall be no less than 100% of the fair market value per ordinary share on the date of grant.
Ordinary shares available for future grant				9,233,414			9,233,414
Options vesting period							4 years
Options expiration term, description							Options granted under the Equity Incentive Plan generally expire after six years from the date of grant.