Acquisitions (Narrative) (Details) - USD ($) $ in Thousands, shares in Millions	Aug. 01, 2023	Mar. 01, 2023	Jul. 01, 2022	Nov. 01, 2021	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Goodwill					$ 1,388,243	$ 1,326,548
Institutional Group [Member]
Business Acquisition [Line Items]
Goodwill					$ 1,053,234	991,539
Sierra Pacific Securities, LLC [Member]
Business Acquisition [Line Items]
Date of acquisition	Aug. 01, 2023
Payments to Acquire Intangible Assets	$ 18,100
Sierra Pacific Securities, LLC [Member] | Institutional Group [Member]
Business Acquisition [Line Items]
Goodwill	$ 6,600
Torreya Partners, LLC [Member]
Business Acquisition [Line Items]
Date of acquisition		Mar. 01, 2023
Payments to Acquire Intangible Assets		$ 5,300
Torreya Partners, LLC [Member] | Institutional Group [Member]
Business Acquisition [Line Items]
Goodwill		$ 55,100
ACXIT Capital Partners [Member]
Business Acquisition [Line Items]
Date of acquisition			Jul. 01, 2022
Payments to Acquire Intangible Assets			$ 5,000
Period of contingent consideration			1 year
Liability for earn-out payments						$ 5,200
ACXIT Capital Partners [Member] | Institutional Group [Member]
Business Acquisition [Line Items]
Goodwill			$ 17,300
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				$ 127,000