Segment Information - Reported Revenue and Profit Before Income Taxes (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Total revenue		$ (264,973)	$ (226,220)	$ (215,884)	$ (213,261)	$ (218,945)	$ (211,804)	$ (212,074)	$ (214,956)	$ (920,338)	$ (857,779)	$ (897,801)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations		$ 16,570	$ 11,828	$ (1,637)	$ (7,025)	$ (7,496)	$ (1,810)	$ (5,246)	$ (7,340)	19,736	(21,892)	(2,428)
Private Client Division
Revenue
Total revenue	[1]									(592,753)	(504,192)	(521,526)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations	[1]									$ 128,840	$ 66,072	$ 59,016
Asset management fees										90.00%	77.50%	77.50%
Asset Management
Revenue
Total revenue	[1]									$ (89,896)	$ (92,852)	$ (97,121)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations	[1]									$ 26,685	$ 31,412	$ 33,133
Asset management fees										10.00%	22.50%	22.50%
Capital markets
Revenue
Total revenue										$ (231,632)	$ (254,933)	$ (279,589)
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations										(39,978)	(17,713)	5,167
Corporate/Other
Revenue
Total revenue										(6,057)	(5,802)	435
Income (loss) before income taxes
Income (loss) before income taxes from continuing operations										$ (95,811)	$ (101,663)	$ (99,744)

[1] Clients investing in the OAM advisory program are charged fees based on the value of assets under management. Advisory fees were allocated 22.5% to the Asset Management and 77.5% to the Private Client segments.