Document and Entity Information	3 Months Ended
	Mar. 31, 2012	Apr. 25, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	MARKETAXESS HOLDINGS INC
Entity Central Index Key	0001278021
Document Type	10-Q
Document Period End Date	Mar. 31, 2012
Amendment Flag	true
Amendment Description	EXPLANATORY NOTE - This Amendment No. 1 to the Quarterly Report on Form 10-Q/A of MARKETAXESS HOLDINGS INC (the "Company") for the quarterly period ended March 31, 2012 is being filed solely to furnish the XBRL exhibits noted in the Exhibit Index hereto as furnished, not filed, herewith, which were incomplete in the initial filing of the Company's Quarterly Report on Form 10-Q on April 26, 2012 (the "Original Filing"). This amendment does not otherwise change or update the disclosure set forth in the Original Filing or otherwise reflect events occurring after the date thereof.
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		36,498,912