Segment Information - Segment's Contribution with Respect to Net Revenue, Operating Expenses, Operating Income (Loss) and Total Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net Revenue	$ 608,908	$ 573,518	$ 1,641,806	$ 1,760,359
Operating Expenses	459,916	2,774	1,281,201	1,916,328
Operating Income (Loss)	148,992	570,744	360,605	(155,969)
Total Assets	4,302,303		4,302,303		$ 4,477,774
Operating Segments [Member] | Financial Advisory Segment [Member]
Segment Reporting Information [Line Items]
Net Revenue	343,488	330,832	896,467	948,735
Operating Expenses	258,865	261,952	719,670	758,108
Operating Income (Loss)	84,623	68,880	176,797	190,627
Total Assets	757,966		757,966		763,374
Operating Segments [Member] | Asset Management Segment [Member]
Segment Reporting Information [Line Items]
Net Revenue	267,725	264,581	767,610	850,226
Operating Expenses	185,753	179,155	543,616	554,738
Operating Income (Loss)	81,972	85,426	223,994	295,488
Total Assets	620,554		620,554		640,034
Corporate [Member]
Segment Reporting Information [Line Items]
Net Revenue	(2,305)	(21,895)	(22,271)	(38,602)
Operating Expenses	15,298	(438,333)	17,915	603,482
Operating Income (Loss)	(17,603)	$ 416,438	(40,186)	$ (642,084)
Total Assets	$ 2,923,783		$ 2,923,783		$ 3,074,366