Segment Information - Reported Revenue and Profit Before Income Taxes (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016		Jun. 30, 2017	Jun. 30, 2016		Dec. 31, 2016
Revenue
Revenue		$ 215,884	$ 212,074	[1]	$ 429,145	$ 427,030	[1]
Income (loss) before income taxes
Total income (loss) before income taxes		(1,637)	(5,246)	[1]	(8,662)	(12,586)	[1]
Private Client Division [Member]
Segment Reporting Information [Line Items]
Revenue Allocation Percentage prior to January 1, 2017								77.50%
Revenue
Revenue	[2]	140,252	121,358		277,641	248,902
Income (loss) before income taxes
Total income (loss) before income taxes	[2]	$ 28,051	$ 14,345		$ 56,813	$ 30,662
Asset management fees		90.00%	77.50%		90.00%	77.50%
Asset Management [Member]
Segment Reporting Information [Line Items]
Revenue Allocation Percentage prior to January 1, 2017								22.50%
Revenue
Revenue	[2]	$ 19,304	$ 22,770		$ 37,970	$ 45,744
Income (loss) before income taxes
Total income (loss) before income taxes	[2]	$ 4,081	$ 5,703		$ 7,792	$ 12,471
Asset management fees		10.00%	22.50%		10.00%	22.50%
Capital Markets [Member]
Revenue
Revenue		$ 53,707	$ 65,524		$ 109,610	$ 126,589
Income (loss) before income taxes
Total income (loss) before income taxes		(10,982)	4,045		(23,596)	(2,753)
Corporate and Other [Member]
Revenue
Revenue		2,621	2,422		3,924	5,795
Income (loss) before income taxes
Total income (loss) before income taxes		$ (22,787)	$ (29,339)		$ (49,671)	$ (52,966)

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[2] Advisory fees were allocated 22.5% to the Asset Management and 77.5% to the Private Client segments.