v3.26.1
SEGMENT REPORTING - Summarized Financial Information by Reportable Segment (Details)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
Mar. 31, 2026
USD ($)
Jun. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Jun. 30, 2026
USD ($)
segment
Jun. 30, 2025
USD ($)
Segment Reporting            
Number of reportable segments | segment         5  
Revenues $ 1,442.8   $ 1,173.5   $ 2,715.6 $ 2,368.5
Cost of revenues 711.2   586.2   1,255.1 1,216.0
Revenues less cost of revenues 731.6   587.3   1,460.5 1,152.5
Depreciation and amortization 28.1   29.9   57.6 60.2
Other segment operating expenses 227.5   218.3   421.3 399.3
Operating income 476.0   339.1   981.6 693.0
Non-operating income (expenses):            
Interest expense (13.2)   (12.9)   (26.5) (25.7)
Interest income 18.2   11.3   35.9 19.7
Earnings on investments, net 12.8   (1.1)   12.1 (4.4)
Other income (expense), net 0.9   (1.8)   7.1 2.2
Income before income tax provision 494.7   334.6   1,010.2 684.8
Income tax provision (benefit) 141.6   99.5   271.4 199.1
Net income (loss) 353.1 $ 385.7 235.1 $ 250.6 738.8 485.7
Options            
Segment Reporting            
Revenues 743.1   575.8   1,411.5 1,160.4
North American Equities            
Segment Reporting            
Revenues 520.0   441.8   935.7 901.9
Europe and Asia Pacific            
Segment Reporting            
Revenues 117.8   99.0   237.2 192.1
Futures            
Segment Reporting            
Revenues 33.4   32.5   72.3 67.8
Global FX            
Segment Reporting            
Revenues 28.5   24.4   58.9 46.3
Operating Segments | Options            
Segment Reporting            
Revenues 743.1   575.8   1,411.5 1,160.4
Cost of revenues 269.2   211.0   470.0 443.2
Revenues less cost of revenues 473.9   364.8   941.5 717.2
Depreciation and amortization 8.6   7.0   16.8 13.9
Other segment operating expenses 124.3   97.9   224.1 185.5
Operating income 341.0   259.9   700.6 517.8
Non-operating income (expenses):            
Interest expense 0.0   0.0   0.0 0.0
Interest income 0.0   0.2   0.0 0.4
Earnings on investments, net 0.0   0.0   0.0 0.0
Other income (expense), net 0.0   (1.4)   0.2 (1.4)
Income before income tax provision 341.0   258.7   700.8 516.8
Income tax provision (benefit) 0.0   0.0   0.0 0.1
Net income (loss) 341.0   258.7   700.8 516.7
Operating Segments | North American Equities            
Segment Reporting            
Revenues 520.0   441.8   935.7 901.9
Cost of revenues 405.3   343.4   709.8 708.9
Revenues less cost of revenues 114.7   98.4   225.9 193.0
Depreciation and amortization 10.2   11.5   21.6 23.5
Other segment operating expenses 38.4   39.6   71.7 77.8
Operating income 66.1   47.3   132.6 91.7
Non-operating income (expenses):            
Interest expense 0.0   0.0   0.0 0.0
Interest income 0.9   0.9   1.7 1.6
Earnings on investments, net 0.0   0.3   (0.3) 0.6
Other income (expense), net 0.5   (0.6)   0.6 (1.2)
Income before income tax provision 67.5   47.9   134.6 92.7
Income tax provision (benefit) 1.2   0.8   2.4 1.7
Net income (loss) 66.3   47.1   132.2 91.0
Operating Segments | Europe and Asia Pacific            
Segment Reporting            
Revenues 117.8   99.0   237.2 192.1
Cost of revenues 33.0   28.6   67.5 57.6
Revenues less cost of revenues 84.8   70.4   169.7 134.5
Depreciation and amortization 6.1   8.1   12.8 16.0
Other segment operating expenses 37.1   57.5   75.6 91.7
Operating income 41.6   4.8   81.3 26.8
Non-operating income (expenses):            
Interest expense (2.3)   (2.0)   (4.7) (3.8)
Interest income 1.1   1.0   2.2 2.1
Earnings on investments, net 0.0   0.0   0.0 0.0
Other income (expense), net (0.1)   (0.1)   (0.5) (0.3)
Income before income tax provision 40.3   3.7   78.3 24.8
Income tax provision (benefit) 1.4   1.0   1.4 1.0
Net income (loss) 38.9   2.7   76.9 23.8
Operating Segments | Futures            
Segment Reporting            
Revenues 33.4   32.5   72.3 67.8
Cost of revenues 2.8   2.4   5.9 4.9
Revenues less cost of revenues 30.6   30.1   66.4 62.9
Depreciation and amortization 0.7   0.5   1.3 1.1
Other segment operating expenses 13.8   12.5   24.9 24.1
Operating income 16.1   17.1   40.2 37.7
Non-operating income (expenses):            
Interest expense 0.0   0.0   0.0 0.0
Interest income 0.5   0.6   1.0 1.2
Earnings on investments, net 0.0   0.0   0.0 0.0
Other income (expense), net 0.0   0.0   0.0 0.0
Income before income tax provision 16.6   17.7   41.2 38.9
Income tax provision (benefit) 0.0   0.0   0.0 0.0
Net income (loss) 16.6   17.7   41.2 38.9
Operating Segments | Global FX            
Segment Reporting            
Revenues 28.5   24.4   58.9 46.3
Cost of revenues 0.9   0.8   1.9 1.4
Revenues less cost of revenues 27.6   23.6   57.0 44.9
Depreciation and amortization 2.4   2.7   5.0 5.6
Other segment operating expenses 9.7   8.4   18.7 16.5
Operating income 15.5   12.5   33.3 22.8
Non-operating income (expenses):            
Interest expense 0.0   0.0   0.0 0.0
Interest income 0.0   0.1   0.0 0.1
Earnings on investments, net 0.0   0.0   0.0 0.0
Other income (expense), net 0.0   0.0   0.0 0.2
Income before income tax provision 15.5   12.6   33.3 23.1
Income tax provision (benefit) 0.0   0.0   0.0 (0.1)
Net income (loss) 15.5   12.6   33.3 23.2
Corporate Items and Eliminations            
Segment Reporting            
Revenues 0.0   0.0   0.0 0.0
Cost of revenues 0.0   0.0   0.0 0.0
Revenues less cost of revenues 0.0   0.0   0.0 0.0
Depreciation and amortization 0.1   0.1   0.1 0.1
Other segment operating expenses 4.2   2.4   6.3 3.7
Operating income (4.3)   (2.5)   (6.4) (3.8)
Non-operating income (expenses):            
Interest expense (10.9)   (10.9)   (21.8) (21.9)
Interest income 15.7   8.5   31.0 14.3
Earnings on investments, net 12.8   (1.4)   12.4 (5.0)
Other income (expense), net 0.5   0.3   6.8 4.9
Income before income tax provision 13.8   (6.0)   22.0 (11.5)
Income tax provision (benefit) 139.0   97.7   267.6 196.4
Net income (loss) $ (125.2)   $ (103.7)   $ (245.6) $ (207.9)