Business Changes and Developments - Goodwill Associated with Acquisitions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Balance at beginning of period	$ 131,387	$ 134,231
Foreign Currency Translation and Other	2,292	(2,844)
Goodwill, Impairment Loss	(2,921)
Balance at end of period	130,758	131,387	$ 134,231
Goodwill, Impaired, Accumulated Impairment Loss	38,528	35,607	35,607
Goodwill, Gross	169,286	166,994	169,838
Investment Banking [Member]
Goodwill [Roll Forward]
Balance at beginning of period	120,464	123,308
Foreign Currency Translation and Other	2,292	(2,844)
Goodwill, Impairment Loss	0
Balance at end of period	122,756	120,464	123,308
Investment Management [Member]
Goodwill [Roll Forward]
Balance at beginning of period	10,923	10,923
Foreign Currency Translation and Other	0	0
Goodwill, Impairment Loss	(2,921)
Balance at end of period	$ 8,002	$ 10,923	$ 10,923