Segment Information - Reported Revenue and Profit Before Income Taxes (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue
Total revenue		$ (295,881)	$ (234,793)	$ (250,935)	$ (251,770)	$ (243,254)	$ (237,814)	$ (242,556)	$ (234,530)	$ (1,033,379)	$ (958,154)	$ (920,338)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations		$ 34,973	$ 6,496	$ 17,391	$ 16,052	$ 15,577	$ 7,154	$ 12,517	$ 9,621	74,912	44,869	19,552
Private Client Division
Revenue
Total revenue	[1]									(653,409)	(617,871)	(592,753)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations	[1]									$ 163,917	$ 149,097	$ 128,840
Asset management fees										90.00%	90.00%	77.50%
Asset Management
Revenue
Total revenue	[1]									$ (88,755)	$ (71,696)	$ (89,896)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations	[1]									$ 31,606	$ 18,590	$ 26,685
Asset management fees										10.00%	10.00%	22.50%
Capital markets
Revenue
Total revenue										$ (290,830)	$ (272,719)	$ (231,632)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations										(13,724)	(13,416)	(39,978)
Corporate/Other
Revenue
Total revenue										(385)	4,132	(6,057)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations										$ (106,887)	$ (109,402)	$ (95,995)

[1] (1) Clients investing in the OAM advisory program are charged fees based on the value of AUM. Advisory fees were allocated 10.0% to the Asset Management and 90.0% to the Private Client segments.