Business Changes and Developments - Intangible Assets Associated with Acquisitions (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 9,595	$ 51,595
Accumulated Amortization	7,292	41,217
Investment Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,320	47,320
Accumulated Amortization	4,159	38,523
Investment Management [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,275	4,275
Accumulated Amortization	3,133	2,694
Client Related [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,830	45,830
Accumulated Amortization	2,743	37,716
Client Related [Member] | Investment Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	42,000
Accumulated Amortization	0	35,356
Client Related [Member] | Investment Management [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,830	3,830
Accumulated Amortization	2,743	2,360
Other Intangible Assets Associated With Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,765	5,765
Accumulated Amortization	4,549	3,501
Other Intangible Assets Associated With Acquisition [Member] | Investment Banking [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,320	5,320
Accumulated Amortization	4,159	3,167
Other Intangible Assets Associated With Acquisition [Member] | Investment Management [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	445	445
Accumulated Amortization	$ 390	$ 334