v2.4.0.6
Defined Contribution and Employee Incentive Plan Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended 71 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Mar. 31, 2013
May 03, 2007
Dec. 31, 2006
Defined contribution and employee incentive plan additional information            
ROI Dollar Unit Payable   $ 7,700,000 $ 7,600,000      
Vested balance of ROI payable   7,700,000 7,600,000      
ROI dollar compensation expense 100,000 100,000        
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         38,143,000  
Vesting Percentage    
·
10% on the date of the IPO (or on the first anniversary of the IPO, in the case of U.S. ROI Unit holders who made the above referenced elections after December 31, 2006); and
 
 
·
an additional 15% on each of the following six anniversaries of the first vesting, assuming continued employment with IBG, Inc. and compliance with non-competition and other applicable covenants.
      
Fair Value ROI Accrual           17,806,000
Compensation Expense, ROI Unit Stock Plan   900,000        
Maximum shares of stock distributable under 2007 Stock Incentive Plan   20,000,000        
Shares granted to external directors       20,423    
2007 Stock Incentive Plan Compensation Expense 8,700,000 19,600,000        
Estimated Future 2007 Stock Incentive Plan Compensation Expense   $ 39,600,000        
Over 59 percent of shares eligible         100.00%  
Percent of shares forfeited post employment         50.00%  
Former employees vesting schedule (Years)         5  
Post employment vesting percentage (Years 1 - 4)         12.50%  
Post employment vesting percentage (Year 5)         50.00%  
Post employment shares distribution       49,893