Parent Company Information - Condensed Statements of Operations and Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Expenses
Employee compensation and benefits	$ 182,104	$ 170,916	$ 156,885
Depreciation and amortization	61,446	53,447	35,996
Professional and consulting fees	33,949	41,925	32,304
General and administrative	19,200	14,501	12,697
Total expenses	391,424	361,716	314,397
Operating income (loss)	326,876	337,235	374,728
Other income (expense)
Interest income	5,040	401	2,446
Interest expense	(700)	(842)	(1,142)
Other, net	5,946	(2,871)	(1,673)
Total other income (expense)	11,412	(3,312)	(369)
Benefit from income taxes	88,064	76,035	74,982
Net income	250,224	257,888	299,377
Comprehensive income	225,857	249,208	304,997
MarketAxess Holdings Inc. (Parent) [Member]
Dividends from subsidiaries	257,200	173,000	30,000
Expenses
Employee compensation and benefits	17,655	17,887	19,710
Depreciation and amortization	2,136	2,123	2,068
Professional and consulting fees	5,528	7,081	7,332
General and administrative	3,081	3,620	2,723
Total expenses	28,400	30,711	31,833
Operating income (loss)	228,800	142,289	(1,833)
Other income (expense)
Interest income	272	132	2,799
Interest expense	(271)	0	(805)
Equity in earnings of unconsolidated affiliate	1,126	0	0
Other, net	(2,633)	(2,950)	(318)
Total other income (expense)	(1,506)	(2,818)	1,676
Income (loss) before income taxes and equity in undistributed earnings of subsidiaries	227,294	139,471	(157)
Benefit from income taxes	(7,710)	(6,472)	(23,444)
Income before equity in undistributed income of subsidiaries	235,004	145,943	23,287
Equity in undistributed income of subsidiaries	15,220	111,945	276,090
Net income	250,224	257,888	299,377
Other comprehensive income (loss), net	(24,367)	(8,680)	5,620
Comprehensive income	$ 225,857	$ 249,208	$ 304,997