Parent Company Information - Condensed Statements of Financial Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
ASSETS
Cash and cash equivalents	$ 506,735	$ 460,858
Investments, at fair value	36,078	28,111
Accounts receivable	63,881	79,577
Intangible assets, net of accumulated amortization	116,377	95,354
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	96,061	85,204
Operating lease right-of-use assets	70,960	75,924
Prepaid expenses and other assets	27,066	29,039
Total assets	1,530,452	1,331,429
Liabilities
Accrued employee compensation	59,719	62,326
Income and other tax liabilities	40,456	42,750
Accounts payable, accrued expenses and other liabilities	71,218	44,354
Operating lease liabilities	88,425	93,612
Total liabilities	489,143	376,368
Stockholders' equity
Preferred stock
Common stock	123	123
Additional paid-in capital	330,262	329,742
Treasury stock	232,712	169,523
Retained earnings	956,966	799,369
Accumulated other comprehensive loss	(13,330)	(4,650)
Total stockholders' equity	1,041,309	955,061	$ 770,091	$ 607,878
Total liabilities and stockholders' equity	1,530,452	1,331,429
MarketAxess Holdings Inc. (Parent) [Member]
ASSETS
Cash and cash equivalents	61,820	55,747
Investments, at fair value	6,327	4,811
Accounts receivable		178
Receivable from subsidiaries	3,488	41,986
Intangible assets, net of accumulated amortization	25	27
Furniture, equipment, leasehold improvements and capitalized software, net of accumulated depreciation and amortization	21,596	23,518
Operating lease right-of-use assets	60,753	64,460
Investments in subsidiaries	982,029	853,626
Prepaid expenses and other assets	4,810	4,591
Income and other tax receivable	1,763	9,028
Total assets	1,142,611	1,057,972
Liabilities
Accrued employee compensation	11,065	10,241
Income and other tax liabilities	5,026	3,457
Accounts payable, accrued expenses and other liabilities	9,233	9,341
Operating lease liabilities	75,978	79,872
Total liabilities	101,302	102,911
Stockholders' equity
Preferred stock
Common stock	123	123
Additional paid-in capital	330,262	329,742
Treasury stock	(232,712)	(169,523)
Retained earnings	956,966	799,369
Accumulated other comprehensive loss	(13,330)	(4,650)
Total stockholders' equity	1,041,309	955,061
Total liabilities and stockholders' equity	1,142,611	1,057,972
Series A Preferred Stock [Member]
Stockholders' equity
Preferred stock
Series A Preferred Stock [Member] | MarketAxess Holdings Inc. (Parent) [Member]
Stockholders' equity
Preferred stock