Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Mar. 02, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Entity Registrant Name	Miragen Therapeutics, Inc.
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	MGEN
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Public Float			$ 56.5
Entity Common Stock, Shares Outstanding		53,066,099
Entity Central Index Key	0001590750
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Shell Company	false