Related Party Transactions - Schedule of Affiliates were Included in the Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Revenue:
Total revenue	$ 617,764	$ 509,677
Expenses
Employee compensation and benefits	197,793	176,877
Technology and communications	39,549	28,728
Professional fees	12,324	12,458
Occupancy	8,192	5,074
Other income (loss), net	$ (1,156)	4,221
iAltaA Capital Markets, LLC
Expenses
Equity method investment percentage	50.00%
MAXEX, LLC
Expenses
Equity method investment percentage	9.00%
Affiliated Entity
Expenses
Employee compensation and benefits	$ (47)	0
Technology and communications	7,007	2,140
General and administrative	0	2
Professional fees	0	76
Occupancy	20	23
Other income (loss), net	$ (429)	0
Affiliated Entity \| iAltaA Capital Markets, LLC
Expenses
Equity method investment percentage	50.00%
Subscription fees
Revenue:
Total revenue	$ 60,273	55,777
Subscription fees \| Affiliated Entity
Revenue:
Total revenue	292	326
LSEG market data fees
Revenue:
Total revenue	26,742	28,925
LSEG market data fees \| Affiliated Entity
Revenue:
Total revenue	26,742	28,925
Other fees
Revenue:
Total revenue	6,916	3,631
Other fees \| Affiliated Entity
Revenue:
Total revenue	$ 126	$ 147

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