Line items represent reporting 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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Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

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Amount, after adjustment, of cost-method investment. Adjustments include, but are not limited to, dividends received in excess of earnings after date of investment that are considered a return of investment and other than temporary impairments.

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The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

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Cost method investment ownership percentage.

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Original fully diluted ownership interest percentage.

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Number of Series A Preferred Shares purchased in AdvisorEngine.

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Number of shares awarded in Thesys Series Y Preferred Shares.

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Investment, Carried at Cost - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 20, 2017	Jun. 30, 2019	Dec. 31, 2018
Investment [Line Items]
Carrying value of investmet		$ 28,080	$ 28,080
AdvisorEngine [Member]
Investment [Line Items]
Ownership interest percentage		46.00%
Original fully diluted ownership interest percentage		41.00%
AdvisorEngine [Member] \| Convertible Preferred Stock [Member]
Investment [Line Items]
Carrying value of investmet		$ 25,000	25,000
AdvisorEngine [Member] \| Convertible Preferred Stock [Member] \| Series A Preferred Stock [Member]
Investment [Line Items]
Number of shares purchased		11,811,856
Non-cumulative dividend		6.00%
AdvisorEngine [Member] \| Convertible Preferred Stock [Member] \| Series A- One Convertible Preferred Stock [Member]
Investment [Line Items]
Number of shares purchased		2,646,062
Thesys Group, Inc [Member]
Investment [Line Items]
Carrying value of investmet		$ 3,080	$ 3,080
Thesys Group, Inc [Member] \| Convertible Preferred Stock [Member] \| Series Y Preferred Stock [Member]
Investment [Line Items]
Number of shares issued	7,797,533
Current fully diluted ownership percentage	19.00%
Liquidation preference	$ 0.231
Thesys Group, Inc [Member] \| Warrant [Member] \| Series Y Preferred Stock [Member]
Investment [Line Items]
Warrants to purchase shares	3,898,766
Exercisable percentage of warrant if claim brought against Company	100.00%