Amount of contribution of other party to the joint venture that the company accounts as equity investment.

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Number of directors in the board of directors of Matrix appointed by the company.

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Number of directors in the board of directors of Matrix appointed by Optech.

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Percentage ownership of other party in the joint venture for their new contribution.

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Percentage ownership of subsidiary in Joint Venture is sold during the period.

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Amount of value received by Joint Venture from selling a portion of subsidiary in Joint Venture during the period.

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

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Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The amount of assets reported by an equity method investment of the entity.

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Equity Investment (Details) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
Equity Investment (Details) $ in Thousands	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) director	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Feb. 28, 2018 USD ($)	Dec. 31, 2015 USD ($)
Ownership percentage for equity method investments						20.00%					20.00%
Revenues		$ 128,746	$ 120,769	$ 128,477	$ 131,484	$ 126,747	$ 114,531	$ 121,581	$ 120,835	$ 509,476	$ 483,694	$ 469,052
Number of directors in the board of directors of Matrix appointed by Optech \| director										2
Number of directors in the board of directors of Matrix appointed by the company \| director										1
Cash and restricted cash		281,446				$ 306,051				$ 281,446	306,051	$ 318,330		$ 368,505
Gain or loss was recognized on investment		0								0
Legal Fees		8,000		$ 1,200
Non-cash gain										608
ITG Derivatives
Revenues											$ 5,300
Matrix Holding Group
Gain or loss was recognized on investment		600								600
Legal Fees							$ 800
Initial investment		$ 1,800								$ 1,800			$ 2,000
Matrix Holding Group \| Cash and restricted cash
Initial investment													600
Matrix Holding Group \| Non-cash assets
Initial investment													$ 1,400
Matrix Holding Group \| Subsequent event
Ownership percentage for equity method investments	10.00%
Gain or loss was recognized on investment	$ 1,300
MH II
Ownership percentage for equity method investments		17.00%								17.00%
Contribution of other party to the joint venture										$ 5,000
Percentage ownership of other party in the joint venture for their new contribution		17.00%								17.00%
MH II \| Subsequent event
Percentage ownership of subsidiary in Joint Venture sold	34.00%
Value received by Joint Venture from selling a portion of subsidiary in Joint Venture	$ 10,000