Business Segment and Geographic Information - Revenue by Client Sector (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Segment and Geographic Information
Financial Designation, Predecessor and Successor [Fixed List]		Predecessor		Predecessor
Gross revenues	$ 200,981	$ 165,253	$ 578,258	$ 505,771
Contingent consideration		2,537		(26,830)
Net revenue	200,981	167,790	578,258	478,941
Operating expenses	142,723	114,973	442,768	338,607
Operating income	58,258	52,817	135,490	140,334
Institutional
Business Segment and Geographic Information
Gross revenues	120,858	97,503	341,167	301,918
Wholesale
Business Segment and Geographic Information
Gross revenues	43,040	34,168	124,416	99,028
Retail
Business Segment and Geographic Information
Gross revenues	20,169	17,812	61,314	57,766
Market Data
Business Segment and Geographic Information
Gross revenues	$ 16,914	$ 15,770	$ 51,361	$ 47,059

Contingent consideration to related parties.

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- Definition

Total costs of sales and operating expenses for the period.

+ References

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- Definition

Indicates designation of financial information when substantially all business or separately identifiable line of business transfers from one entity to another entity. Acceptable values are "Predecessor" and "Successor".

+ References

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

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-Publisher FASB
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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

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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.

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No definition available.

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