Segment Information - Segment's Contribution with Respect to Net Revenue, Operating Expenses, Operating Income (Loss) and Total Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Net Revenue (Expense)	$ 612,690	$ 480,354	$ 490,405	$ 401,903	$ 560,693	$ 428,806	$ 436,910	$ 486,039	$ 1,985,352	$ 1,912,448	$ 1,829,512
Operating Expenses	539,536	399,236	449,467	380,306	565,890	382,080	392,377	448,216	1,768,545	1,788,563	1,594,013
Operating Income (Loss)	73,154	81,118	40,938	21,597	(5,197)	46,726	44,533	37,823	216,807	123,885	235,499
Total Assets	3,011,137				2,986,893				3,011,137	2,986,893	3,081,936
Financial Advisory [Member]
Segment Reporting Information [Line Items]
Net Revenue (Expense)									980,577	1,049,090	992,107
Operating Expenses									959,668	1,057,620	929,688
Operating Income (Loss)									20,909	(8,530)	62,419
Total Assets	714,708				793,007				714,708	793,007	767,699
Asset Management [Member]
Segment Reporting Information [Line Items]
Net Revenue (Expense)									1,039,130	896,260	897,401
Operating Expenses									704,045	659,502	628,945
Operating Income (Loss)									335,085	236,758	268,456
Total Assets	612,018				566,677				612,018	566,677	583,524
Corporate [Member]
Segment Reporting Information [Line Items]
Net Revenue (Expense)									(34,355)	(32,902)	(59,996)
Operating Expenses									104,832	71,441	35,380
Operating Income (Loss)									(139,187)	(104,343)	(95,376)
Total Assets	$ 1,684,411				$ 1,627,209				$ 1,684,411	$ 1,627,209	$ 1,730,713