Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Mar. 15, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	ARCA Biopharma, Inc.
Entity Central Index Key	0000907654
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Period Focus	FY
Trading Symbol	ABIO
Document Fiscal Year Focus	2015
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Smaller Reporting Company
Entity Public Float			$ 47,901,952
Entity Common Stock, Shares Outstanding		9,056,647