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Organization Of Business (Details)	9 Months Ended
	Sep. 30, 2018 employee segment	Jul. 26, 2018	May 03, 2007
Number of employees | employee	1,380
Number of operating segments | segment	2
IBG LLC [Member]
IBG Inc. ownership % of IBG LLC	18.10%	17.80%	10.00%

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Number of persons employed by the Entity

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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