Parent Company Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net Income (Loss)	$ 258,055	$ 250,224	$ 257,888
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	70,557	61,446	53,447
Amortization of operating lease right-of-use assets	5,853	5,708	6,799
Stock-based compensation expense	29,190	29,864	27,314
Deferred taxes	(5,815)	(6,547)	3,118
Other	(3,113)	555	(466)
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(7,116)	(15,136)	15,598
Decrease/(increase) in prepaid expenses and other assets	(11,898)	(4,249)	2,214
(Decrease) increase in accrued employee compensation	1,466	(3,417)	(2,607)
Increase (decrease) in income and other tax liabilities	(14,691)	(4,768)	(5,638)
(Decrease)/increase in accounts payable, accrued expenses and other liabilities	(7,229)	11,384	215
(Decrease) in operating lease liabilities	(6,735)	(6,373)	(7,001)
Net cash provided by operating activities	333,767	289,231	282,091
Cash flows from investing activities
Acquisitions, net of cash and cash equivalents acquired	(78,476)	0	(17,078)
Acquisition of equity method investment	0	(34,400)	0
Proceeds from maturities and sales	4,452	0	0
Purchases	(28,818)	0	0
Purchases of furniture, equipment and leasehold improvements	(9,326)	(13,142)	(17,493)
Net cash (used in) investing activities	(155,290)	(86,272)	(67,694)
Cash flows from financing activities
Cash dividend on common stock	(109,658)	(105,942)	(99,792)
Exercise of stock options	940	672	7,096
Withholding tax payments on restricted stock vesting and stock option exercises	(25,839)	(23,404)	(33,890)
Repurchases of common stock	0	(87,540)	(63,189)
Proceeds from short-term borrowings	123,995	100,000	70,348
Repayments of short-term borrowings	(123,995)	(100,000)	(70,348)
Net cash (used in) financing activities	(147,057)	(242,378)	(189,775)
Effect of exchange rate changes on investments	7,588	(13,484)	(7,105)
Cash and cash equivalents including restricted cash
Net increase (decrease) for the period	39,008	(52,903)	17,517
Beginning of period	572,664	625,567	608,050
End of period	611,672	572,664	625,567
Supplemental cash flow information:
Cash paid for income taxes	94,814	88,677	70,003
Cash paid for interest	1,870	652	830
Non-cash investing and financing activity:
Exercise of stock options - cashless	0	3,845	2,750
Right-of-use assets obtained in exchange for operating lease liabilities	1,183	1,880	1,972
Treasury stock used for acquisition of business	(43,841)	0	0
MarketAxess Holdings Inc. (Parent) [Member]
Cash flows from operating activities
Net Income (Loss)	258,055	250,224	257,888
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,153	2,136	2,123
Amortization of operating lease right-of-use assets	3,361	3,347	4,484
Stock-based compensation expense	9,725	12,554	12,706
Deferred taxes	101	(5,076)	1,712
Equity in undistributed income of subsidiaries	(2,221)	(15,220)	(111,945)
Other	(4,675)	441	0
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable	(1,154)	(769)	178
(Increase) decrease in receivable from subsidiaries	(189)	984	(1,516)
Decrease/(increase) in prepaid expenses and other assets	1,296	1,175	219
(Increase) decrease in income and other tax receivables	3,800	(9,711)	7,265
(Decrease) increase in accrued employee compensation	(1,104)	(1,372)	824
Increase (decrease) in income and other tax liabilities	2,287	62	(143)
(Decrease)/increase in accounts payable, accrued expenses and other liabilities	(861)	443	(607)
(Decrease) in operating lease liabilities	(3,624)	(3,689)	(4,673)
Net cash provided by operating activities	272,424	241,110	215,449
Cash flows from investing activities
Acquisitions, net of cash and cash equivalents acquired	(81,161)	0	(17,079)
Acquisition of equity method investment	0	(34,400)	0
Investments in subsidiaries	(10,058)	(8,326)	0
Proceeds from maturities and sales	4,454	0	0
Purchases	(28,818)	0	0
Purchases of furniture, equipment and leasehold improvements	(239)	(96)	(198)
Net cash (used in) investing activities	(115,822)	(42,822)	(17,277)
Cash flows from financing activities
Cash dividend on common stock	(109,658)	(105,942)	(99,791)
Exercise of stock options	940	672	7,096
Withholding tax payments on restricted stock vesting and stock option exercises	(25,839)	(23,404)	(33,890)
Repurchases of common stock	0	(87,540)	(63,189)
Proceeds from short-term borrowings	100,000	100,000	0
Repayments of short-term borrowings	(100,000)	(100,000)	0
Net cash (used in) financing activities	(134,557)	(216,214)	(189,774)
Effect of exchange rate changes on investments	(3)	15	(2,324)
Cash and cash equivalents including restricted cash
Net increase (decrease) for the period	22,042	(17,911)	6,073
Beginning of period	43,909	61,820	55,747
End of period	65,951	43,909	61,820
Supplemental cash flow information:
Cash paid for income taxes	55,784	65,764	41,103
Cash paid for interest	35	271	0
Non-cash investing and financing activity:
Exercise of stock options - cashless	0	3,845	2,750
Right-of-use assets obtained in exchange for operating lease liabilities	1,072	0	0
Treasury stock used for acquisition of business	43,841	0	0
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
(Increase) in trading investments	(1,103)	1,813	(2,306)
Mutual Funds Held In Rabbi Trust [Member] | MarketAxess Holdings Inc. (Parent) [Member]
Changes in operating assets and liabilities:
(Increase) in trading investments	5,474	7,931	47,371
Trading Investments [Member]
Changes in operating assets and liabilities:
(Increase) in trading investments	$ (25,248)	$ (49,527)	$ (5,574)