Net Capital Requirements and Customer Protection Requirements (Details) (USD $)	Dec. 31, 2011
Net Capital Requirements and Customer Protection Requirements
Minimum net capital required	$ 100,000
Marketaxess Corporation [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	73,890,000
Minimum net capital required	2,499,000
Excess net capital	71,391,000
Marketaxess Europe Limited [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	24,301,000
Minimum net capital required	3,179,000
Excess net capital	21,122,000
Marketaxess Canada Limited [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	418,000
Minimum net capital required	269,000
Excess net capital	$ 149,000