Parent Company Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net Income (Loss)	$ 274,181	$ 258,055	$ 250,224
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	73,824	70,557	61,446
Amortization of operating lease right-of-use assets	6,639	5,853	5,708
Stock-based compensation expense	29,684	29,190	29,864
Deferred taxes	(3,878)	(5,815)	(6,547)
Other	7,042	(3,113)	555
Changes in operating assets and liabilities:
(Increase)/decrease in accounts receivable	(3,730)	(7,116)	(15,136)
Decrease/(increase) in prepaid expenses and other assets	1,009	(11,898)	(4,249)
(Decrease) increase in accrued employee compensation	7,049	1,466	(3,417)
Increase (decrease) in income and other tax liabilities	(3,284)	(14,691)	(4,768)
(Decrease)/increase in accounts payable, accrued expenses and other liabilities	3,543	(7,229)	11,384
(Decrease) in operating lease liabilities	(8,730)	(6,735)	(6,373)
Net cash provided by operating activities	385,237	333,767	289,231
Cash flows from investing activities
Acquisition of equity method investment	0	0	(34,400)
Proceeds from maturities and sales	12,440	4,452	0
Purchases	(42,810)	(28,818)	0
Purchases of furniture, equipment and leasehold improvements	(9,942)	(9,326)	(13,142)
Net cash (used in) investing activities	(86,935)	(155,290)	(86,272)
Cash flows from financing activities
Cash dividends on common stock	(112,697)	(109,658)	(105,942)
Exercise of stock options	2,988	940	672
Withholding tax payments on Full Value Awards vesting and stock option exercises	(16,194)	(25,839)	(23,404)
Repurchases of common stock	(75,474)	0	(87,540)
Proceeds from short-term borrowings	344,925	123,995	100,000
Repayments of short-term borrowings	(344,925)	(123,995)	(100,000)
Net cash (used in) financing activities	(201,377)	(147,057)	(242,378)
Effect of exchange rate changes on cash and cash equivalents	(8,138)	7,588	(13,484)
Cash and cash equivalents including restricted cash
Net increase for the period	88,787	39,008	(52,903)
Beginning of period	611,672	572,664	625,567
End of period	700,459	611,672	572,664
Supplemental cash flow information:
Cash paid for income taxes	96,932	94,814	88,677
Cash paid for interest	1,717	1,870	652
Non-cash investing and financing activity
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	1,840	1,183	1,880
Treasury stock used for acquisition of business	0	(43,841)	0
MarketAxess Holdings Inc. (Parent) [Member]
Cash flows from operating activities
Net Income (Loss)	274,181	258,055	250,224
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,186	2,153	2,136
Amortization of operating lease right-of-use assets	3,697	3,361	3,347
Stock-based compensation expense	7,130	9,725	12,554
Deferred taxes	397	101	(5,076)
Equity in undistributed income of subsidiaries	(42,362)	(2,221)	(15,220)
Other	4,304	(4,675)	441
Changes in operating assets and liabilities:
(Increase)/decrease in accounts receivable	526	(1,154)	(769)
Decrease in receivable from subsidiaries	12,694	5,474	7,931
Decrease/(increase) in prepaid expenses and other assets	304	1,296	(1,175)
(Decrease) increase in accrued employee compensation	1,118	(1,104)	(1,372)
(Increase) decrease in income and other tax receivables	(579)	3,800	(9,711)
Increase (decrease) in income and other tax liabilities	(2,278)	2,287	62
(Decrease)/increase in accounts payable, accrued expenses and other liabilities	4,809	(861)	443
(Decrease) in operating lease liabilities	(4,669)	(3,624)	(3,689)
Net cash provided by operating activities	261,364	272,424	241,110
Cash flows from investing activities
Acquisition of business	0	(81,161)	0
Acquisition of equity method investment	0	0	(34,400)
Investments in subsidiaries	(30)	(10,058)	(8,326)
Proceeds from maturities and sales	12,440	4,454	0
Purchases	(42,810)	(28,818)	0
Purchases of furniture, equipment and leasehold improvements	(156)	(239)	(96)
Net cash (used in) investing activities	(30,556)	(115,822)	(42,822)
Cash flows from financing activities
Cash dividends on common stock	(112,697)	(109,658)	(105,942)
Exercise of stock options	2,988	940	672
Withholding tax payments on Full Value Awards vesting and stock option exercises	(16,194)	(25,839)	(23,404)
Repurchases of common stock	(75,474)	0	(87,540)
Proceeds from short-term borrowings	100,000	100,000	100,000
Repayments of short-term borrowings	(100,000)	(100,000)	(100,000)
Net cash (used in) financing activities	(201,377)	(134,557)	(216,214)
Effect of exchange rate changes on cash and cash equivalents	0	(3)	15
Cash and cash equivalents including restricted cash
Net increase for the period	29,431	22,042	(17,911)
Beginning of period	65,951	43,909	61,820
End of period	95,382	65,951	43,909
Supplemental cash flow information:
Cash paid for income taxes	53,999	55,784	65,764
Cash paid for interest	167	35	271
Non-cash investing and financing activity
Exercise of stock options - cashless	1,735	0	3,845
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	0	1,072	0
Treasury stock used for acquisition of business	0	43,841	0
Mutual Funds Held In Rabbi Trust [Member]
Changes in operating assets and liabilities:
Decrease/(increase) in trading investments	(621)	(1,103)	1,813
Mutual Funds Held In Rabbi Trust [Member] | MarketAxess Holdings Inc. (Parent) [Member]
Changes in operating assets and liabilities:
Decrease/(increase) in trading investments	(94)	(189)	984
Trading Investments [Member]
Changes in operating assets and liabilities:
Decrease/(increase) in trading investments	$ (629)	$ (25,248)	$ (49,527)