Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Fee and other revenue	$ 314.7	$ 305.5
Investment revenue	22.8	2.1
Total revenue	337.5	307.6
COST OF REVENUE
Commissions and other fee expense	149.6	148.7
Investment commissions expense	13.7	0.4
Direct transaction expense	14.6	12.3
Total cost of revenue	177.9	161.4
GROSS PROFIT
Gross Profit, Total	159.6	146.2
OPERATING EXPENSES
Compensation and benefits	61.0	56.5
Transaction and operations support	50.5	45.1
Occupancy, equipment and supplies	15.9	14.5
Depreciation and amortization	12.5	12.2
Total operating expenses	139.9	128.3
OPERATING INCOME	19.7	17.9
Other expenses
Interest expense	15.0	10.9
Other non-operating expense	1.0	0.9
Total other expenses	16.0	11.8
Income before income taxes	3.7	6.1
Income tax (benefit) expense	(1.3)	1.0
NET INCOME	$ 5.0	$ 5.1
EARNINGS PER COMMON SHARE
Basic (usd per share)	$ 0.05	$ 0.05
Diluted (usd per share)	$ 0.05	$ 0.05
Basic	97.2	95.7
Diluted (in shares)	100.7	99.5