Shareholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Aug. 07, 2019	Dec. 05, 2018	Dec. 31, 2019	Dec. 31, 2018	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.
Interest and accretion of discount on convertible notes			$ 568	$ 40
Accrued Interest			$ 32	$ 40
2016 Equity Incentive Plan [Member]
Shareholders' Equity (Textual)
Proceeds received from issuance of ordinary shares	$ 8,019
Aggregate principal amount		$ 10,000
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	$ 3.73	$ 3.90
Maturity date		Dec. 31, 2021
Semi-annual interest payments, description			In June 2019, the Company paid the first of the semi-annual interest payments totaling, $287, of which $215 was paid in cash and the remaining portion through the issuance of 35,950 shares. In December 2019, the Company paid the second of the semi-annual interest payments totaling, $288, of which $216 was paid in cash and the remaining portion through the issuance of 46,532 shares.
Non-Employee Plan [Member]
Shareholders' Equity (Textual)
Ordinary shares available for future grant issuance					1,150,000
Options vesting period			4 years
Options expiration, term			Options granted under the Non-Employee Director Plan generally expire after six years from the date of grant.
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 issuance			8,515,306
Options vesting period			4 years
Options expiration, term			Options granted under the Equity Incentive Plan generally expire after six years from the date of grant.
Non Vested Stock Options [Member]
Shareholders' Equity (Textual)
Unrecognized compensation expense			$ 2,595
Recognized over remaining weighted average period			3 years
Non Vested Stock Options [Member] | Non-Employee Plan [Member]
Shareholders' Equity (Textual)
Ordinary shares available for future grant issuance			1,396,882
Unrecognized compensation expense			$ 2,150
Recognized over remaining weighted average period			3 years 1 month 13 days
Equity Incentive Plans [Member]
Shareholders' Equity (Textual)
Ordinary shares available for future grant issuance					11,200,000