Business combination period of issued shares held in escrow.

No definition available.

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Namespace Prefix:	mktx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Increase in business combination consideration transferred

+ References

No definition available.

+ Details

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Namespace Prefix:	mktx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

+ Details

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Balance Type:	na
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Period when results of operations of the acquired entity are included in the income statement of the combined entity, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
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Balance Type:	credit
Period Type:	duration

- Definition

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

+ References

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
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- Details

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Namespace Prefix:
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Acquisitions - Additional Information (Detail) - LiquidityEdge LLC [Member] - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Nov. 01, 2019	Mar. 31, 2020	Sep. 30, 2020
Business Acquisition [Line Items]
Aggregate consideration	$ 152,700		$ 153,210
Cash consideration	$ 103,900
Business combination, shares of common stock	146,450
Business combination, common stock value	$ 48,800
Increase in aggregate consideration		$ 500
Business combination, period for shares of common stock placed in escrow	18 months
Business combination, shares of common stock received period	6 months
Escrow [Member]
Business Acquisition [Line Items]
Business combination, shares of common stock	43,937