Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Aug. 12, 2014
Document Information [Line Items]
Entity Registrant Name	ARCA Biopharma, Inc.
Entity Central Index Key	0000907654
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2014
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2014
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		21,010,815