Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 503,349	$ 257,484
Management Fees	25,742	11,604
Incentive income	2,258	0
Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	503,106	257,226
Management Fees	25,499	11,346
Incentive income	2,258	0
Asset Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	243	258
Management Fees	243	258
Incentive income	0	0
Underwriting fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	154,304	63,270
Strategic/financial advisory fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	73,555	21,996
Placement and sales agent fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	72,544	17,596
Expense reimbursements from clients | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,431	2,166
Investment banking revenue | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	304,834	105,028
Commissions | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	161,792	132,208
Trade conversion | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,130	4,639
Equity and credit research fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,593	4,005
Brokerage | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 170,515	$ 140,852