Segment Information - Segment's Contribution with Respect to Net Revenue, Operating Expenses, Operating Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Net Revenue (Expense)	$ 533,400	$ 401,903
Operating Expenses	426,220	380,306
Operating Income (Loss)	107,180	21,597
Financial Advisory [Member]
Segment Reporting Information [Line Items]
Net Revenue (Expense)	275,496	168,462
Operating Expenses	245,415	216,908
Operating Income (Loss)	30,081	(48,446)
Asset Management [Member]
Segment Reporting Information [Line Items]
Net Revenue (Expense)	268,564	244,025
Operating Expenses	175,761	155,077
Operating Income (Loss)	92,803	88,948
Corporate [Member]
Segment Reporting Information [Line Items]
Net Revenue (Expense)	(10,660)	(10,584)
Operating Expenses	5,044	8,321
Operating Income (Loss)	$ (15,704)	$ (18,905)