Current Expected Credit Losses (CECL) - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit losses reserve	$ 14.9	$ 2.4	$ 2.6	$ 1.9
Current-period provision for expected credit losses	12.5	(0.2)	0.7
Loans, forgivable loans and other receivables from employees and partners, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit losses reserve	2.5	1.7	1.6	1.1
Current-period provision for expected credit losses	0.8	0.1	0.5
Accrued commissions and other receivables, net
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit losses reserve	5.4	0.7	1.0	$ 0.8
Current-period provision for expected credit losses	4.7	$ (0.3)	$ 0.2
Accrued commissions and other receivables, net | Russia/Ukraine Conflit
Financing Receivable, Allowance for Credit Loss [Line Items]
Current-period provision for expected credit losses	$ 4.5