Acquisitions (Narrative) (Details) - USD ($) $ in Thousands, shares in Millions				12 Months Ended
	Nov. 01, 2021	Sep. 03, 2019	Jul. 01, 2019	Dec. 31, 2020	Dec. 31, 2021
Business Acquisition [Line Items]
Goodwill				$ 1,181,998	$ 1,306,892
Institutional Group [Member]
Business Acquisition [Line Items]
Goodwill				846,989	971,883
Vining Sparks [Member]
Business Acquisition [Line Items]
Date of acquisition	Nov. 01, 2021
Shares issued as part of the consideration	1.2
Payments to Acquire Intangible Assets	$ 25,400
Vining Sparks [Member] | Institutional Group [Member]
Business Acquisition [Line Items]
Goodwill	$ 124,600
B&F Capital Markets, Inc. [Member]
Business Acquisition [Line Items]
Date of acquisition		Sep. 03, 2019
Period of contingent consideration		5 years
Liability for earn-out payments				$ 16,000	10,500
Mooreland Partners [Member]
Business Acquisition [Line Items]
Date of acquisition				Jul. 01, 2019
Period of contingent consideration			3 years
Liability for earn-out payments				$ 13,000	18,500
Additional liability for earn-out payments					$ 13,500