Parent Company Information - Condensed Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues	$ 752,547	$ 718,300	$ 698,951
Expenses
Employee compensation and benefits	206,926	182,104	170,916
Depreciation and amortization	70,557	61,446	53,447
Technology and communications	62,801	52,964	42,474
Professional and consulting fees	31,935	33,949	41,925
Occupancy	14,216	14,121	13,320
General and administrative	23,042	19,200	14,501
Total expenses	437,528	391,424	361,716
Operating income	315,019	326,876	337,235
Other income (expense)
Interest income	22,425	5,040	401
Interest expense	(1,983)	(700)	(842)
Equity in earnings of unconsolidated affiliate	735	1,126	0
Other, net	(3,496)	5,946	(2,871)
Total other income (expense)	17,681	11,412	(3,312)
Benefit from income taxes	74,645	88,064	76,035
Net income	258,055	250,224	257,888
Comprehensive income	271,382	225,857	249,208
MarketAxess Holdings Inc. (Parent) [Member]
Revenues	270,700	257,200	173,000
Expenses
Employee compensation and benefits	13,938	17,655	17,887
Depreciation and amortization	2,153	2,136	2,123
Professional and consulting fees	5,828	5,528	7,081
General and administrative	2,301	3,081	3,620
Total expenses	24,220	28,400	30,711
Operating income	246,480	228,800	142,289
Other income (expense)
Interest income	3,557	272	132
Interest expense	(155)	(271)	0
Equity in earnings of unconsolidated affiliate	735	1,126	0
Other, net	(369)	(2,633)	(2,950)
Total other income (expense)	3,768	(1,506)	(2,818)
Income before income taxes and equity in undistributed earnings of subsidiaries	250,248	227,294	139,471
Benefit from income taxes	(5,586)	(7,710)	(6,472)
Income before equity in undistributed income of subsidiaries	255,834	235,004	145,943
Equity in undistributed income of subsidiaries	2,221	15,220	111,945
Net income	258,055	250,224	257,888
Other comprehensive income (loss), net	13,327	(24,367)	(8,680)
Comprehensive income	$ 271,382	$ 225,857	$ 249,208