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Equity And Earnings Per Share (Tables) | 12 Months Ended
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Dec. 31, 2017
Equity And Earnings Per Share [Abstract] |
IBG LLC Ownership of Member Interests |
﻿ |  |  |  |  |  |
﻿ |  | IBG, Inc. |  | Holdings |  | Total
﻿ | Ownership % | 17.4% |  | 82.6% |  | 100.0%
﻿ | Membership interests | 71,479,604 |  | 340,229,444 |  | 411,709,048
﻿
Earnings Per Share Basic And Diluted | Basic earnings per share is calculated utilizing net income available for common stockholders divided by the weighted average number of shares of Class A and Class B common stock outstanding for that period.
﻿ |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |
﻿ |  | Year-Ended December 31,
﻿ |  | 2017 |  | 2016 |  | 2015
﻿ |  |  |  |  |  |  |  |  |
﻿ |  | (in millions, except share or per share amounts)
﻿Basic earnings per share |  |  |  |  |  |  |  |  |
﻿Net income available for common stockholders |  | $ | 76 |  | $ | 84 |  | $ | 49
﻿Weighted average shares of common stock outstanding |  |  |  |  |  |  |  |  |
﻿Class A |  |  | 69,926,833 |  |  | 66,013,147 |  |  | 61,042,971
﻿Class B |  |  | 100 |  |  | 100 |  |  | 100
﻿ |  |  | 69,926,933 |  |  | 66,013,247 |  |  | 61,043,071
﻿Basic earnings per share |  | $ | 1.09 |  | $ | 1.28 |  | $ | 0.80
﻿ Diluted earnings per share are calculated utilizing the Company’s basic net income available for common stockholders divided by diluted weighted average shares outstanding with no adjustments to net income available to common stockholders for potentially dilutive common shares. ﻿
﻿ |  |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |  |
﻿ |  | Year-Ended December 31,
﻿ |  | 2017 |  | 2016 |  | 2015
﻿ |  | (in millions, except share or per share amounts)
﻿Diluted earnings per share |  |  |  |  |  |  |  |  |
﻿Net income available for common stockholders |  | $ | 76 |  | $ | 84 |  | $ | 49
﻿Weighted average shares of common stock outstanding |  |  |  |  |  |  |  |  |
﻿Class A |  |  |  |  |  |  |  |  |
﻿Issued and outstanding |  |  | 69,926,833 |  |  | 66,013,147 |  |  | 61,042,971
﻿Potentially dilutive common shares |  |  |  |  |  |  |  |  |
﻿Issuable pursuant to employee stock incentive plans |  |  | 977,988 |  |  | 1,286,166 |  |  | 1,466,725
﻿Class B |  |  | 100 |  |  | 100 |  |  | 100
﻿ |  |  | 70,904,921 |  |  | 67,299,413 |  |  | 62,509,796
﻿Diluted earnings per share |  | $ | 1.07 |  | $ | 1.25 |  | $ | 0.78
﻿

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- Definition Tabular disclosure of the ownership of IBG LLC member interests. + References No definition available. + Details
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Data Type: | nonnum:textBlockItemType
Balance Type: | na
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- References No definition available. + Details
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- Definition Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
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