Fair Value of shares issued to IBG LLC, held as treasury stock, in connection with the ROI Dollar Unit Stock Plan.

No definition available.

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- Definition

As of the balance sheet date, the aggregate estimated unrecognized future compensation costs for unvested 2007 Stock Incentive Plan shares.

+ References

No definition available.

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- Definition

The maximum number of shares authorized to be granted and issued under the 2007 Stock Incentive Plan

+ References

No definition available.

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- Definition

Shares distributed under post employment provisions.

+ References

No definition available.

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- Definition

Number of shares granted to external directors under the 2007 Stock Incentive Plan.

+ References

No definition available.

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- Definition

Stock Incentive Plan Granted Shares Adjustment for prior year end

+ References

No definition available.

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- Definition

Number of common shares originally registered and held in treasury to be distributed to employees under the ROI Unit Stock Plan.

+ References

No definition available.

+ Details

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- Definition

Number of common shares issued to IBG LLC and held as treasury stock in connection with the investment of accumulated ROI Dollar Unit earnings at the election of employees. Amount includes 21,009 shares allocated from the 2007 Stock Incentive Plan.

+ References

No definition available.

+ Details

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- Definition

Shares allocated from the 2007 Stock Incentive Plan to cover shares issued under the ROI Unit Stock Plan and held as treasury stock.

+ References

No definition available.

+ Details

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

+ 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.

+ References

No definition available.

+ Details

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- Definition

Percentage of vesting of share-based compensation awards.

+ References

+ Details

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Employee Incentive Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		131 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	May 03, 2007
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
401(k) plan contribution expense	$ 1.0	$ 1.0
Common Stock Shares issued under ROI Unit Stock Plan				1,271,009
ROI Shares issued to IBG LLC				1,250,000
2007 SIP shares issued under ROI Unit Stock Plan				21,009
Fair value ROI Treasury Stock				$ 38.0
Maximum shares of stock distributable under 2007 Stock Incentive Plan	30,000,000		30,000,000
Stock Incentive Plan Granted Shares Adjustment	18,335
2007 Stock Incentive Plan Compensation Expense	$ 14.0	$ 13.0
Estimated Future 2007 Stock Incentive Plan Compensation Expense	$ 34.0		$ 34.0
Post employment shares distribution			578,574
2007 Stock Incentive Plan (Shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting Percentage, description	• 10% on the first vesting date, which is on or about May 9 of each year; and• an additional 15% on each of the following six anniversaries of the first vesting, assuming continued employment with the Company and compliance with non-competition and other applicable covenants.
2007 Stock Incentive Plan (Shares) \| External Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
Shares granted to external directors			24,263
2007 Stock Incentive Plan (Shares) \| Share-based Compensation Award, Tranche One [Member] \| External Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage per year	20.00%