Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 19, 2018
Document And Entity Information
Entity Registrant Name	MGT CAPITAL INVESTMENTS, INC.
Entity Central Index Key	0001001601
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business Flag	true
Entity Emerging Growth Company	false
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		100,576,627
Trading Symbol	MGTI
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2018