Net Capital Requirements and Customer Protection Requirements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Net capital requirements and customer protection requirements
Minimum net capital required	$ (100)
MarketAxess Corporation [Member]
Net capital requirements and customer protection requirements
Net capital	63,624
Minimum net capital required	2,266
Excess net capital	61,358
MarketAxess Europe Limited [Member]
Net capital requirements and customer protection requirements
Net capital	13,151
Minimum net capital required	2,943
Excess net capital	10,208
MarketAxess Canada Limited [Member]
Net capital requirements and customer protection requirements
Net capital	479
Minimum net capital required	277
Excess net capital	$ 202