Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Apr. 14, 2021	Jun. 30, 2020
Cover [Abstract]
Entity Registrant Name	MGT CAPITAL INVESTMENTS, INC.
Entity Central Index Key	0001001601
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business Flag	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 7,578,370
Entity Common Stock, Shares Outstanding		536,649,910
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020