Net Capital Requirements and Customer Protection Requirements (Details) (USD $)	Mar. 31, 2013
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	69,812,000
Minimum net capital required	1,585,000
Excess net capital	68,227,000
MarketAxess Europe Limited [Member]
Net capital requirements and customer protection requirements
Net capital	16,334,000
Minimum net capital required	2,753,000
Excess net capital	13,581,000
MarketAxess Canada Limited [Member]
Net capital requirements and customer protection requirements
Net capital	478,000
Minimum net capital required	270,000
Excess net capital	$ 208,000