Net Capital Requirements and Customer Protection Requirements (Details) (USD $)	Jun. 30, 2012
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	66,293,000
Minimum net capital required	1,619,000
Excess net capital	64,674,000
MarketAxess Europe Limited [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	28,001,000
Minimum net capital required	3,212,000
Excess net capital	24,789,000
MarketAxess Canada Limited [Member]
Net Capital Requirements and Customer Protection Requirements
Net capital	406,000
Minimum net capital required	271,000
Excess net capital	$ 135,000