Parent Company Information - Condensed Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
ASSETS
Cash and cash equivalents	$ 544,478	$ 451,280
Investments, at fair value	165,260	134,861
Accounts receivable	91,845	89,839
Intangible assets, net of accumulated amortization	98,078	119,108
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	107,298	102,671
Operating lease right-of-use assets	58,132	63,045
Prepaid expenses and other assets	82,584	84,499
Total assets	1,789,216	2,015,067
Liabilities
Accrued employee compensation	68,054	60,124
Income and other tax liabilities	3,683	7,892
Accounts payable, accrued expenses and other liabilities	37,320	37,013
Operating lease liabilities	72,654	79,677
Total liabilities	400,556	722,104
Stockholders' equity
Preferred stock	0	0
Common stock voting	123	123
Additional paid-in capital	350,701	333,292
Treasury stock	333,369	260,298
Retained earnings	1,405,904	1,244,216
Accumulated other comprehensive loss	(34,699)	(24,370)
Total stockholders' equity	1,388,660	1,292,963	$ 1,081,093	$ 1,041,309
Total liabilities and stockholders' equity	1,789,216	2,015,067
MarketAxess Holdings Inc. (Parent) [Member]
ASSETS
Cash and cash equivalents	94,332	65,951
Investments, at fair value	60,735	30,225
Accounts receivable	1,397	1,923
Receivable from subsidiaries	22,606	18,010
Intangible assets, net of accumulated amortization	18	21
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	15,617	17,644
Operating lease right-of-use assets	51,416	55,113
Investments in subsidiaries	1,179,524	1,140,798
Prepaid expenses and other assets	40,903	45,140
Income and other tax receivable	8,253	7,674
Total assets	1,474,801	1,382,499
Liabilities
Accrued employee compensation	9,707	8,589
Income and other tax liabilities	722	3,000
Accounts payable, accrued expenses and other liabilities	10,646	8,212
Operating lease liabilities	65,066	69,735
Total liabilities	86,141	89,536
Stockholders' equity
Preferred stock	0	0
Common stock voting	123	123
Additional paid-in capital	350,701	333,292
Treasury stock	(333,369)	(260,298)
Retained earnings	1,405,904	1,244,216
Accumulated other comprehensive loss	(34,699)	(24,370)
Total stockholders' equity	1,388,660	1,292,963
Total liabilities and stockholders' equity	1,474,801	1,382,499
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock	0	0
Series A Preferred Stock [Member] | MarketAxess Holdings Inc. (Parent) [Member]
Stockholders' equity
Preferred stock	$ 0	$ 0