Segment Operating Results (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]
Total Other Revenue, net	$ (885)		$ (1,255)		$ (2,820)		$ (4,681)
Special Charges	0		0		0		662
Total Other Expenses	8,020	[1]	12,735	[1]	28,677	[1]	42,004	[1]
Investment Banking [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	(330)	[2]	(435)	[2]	(966)	[2]	(2,407)	[2]
Interest expense on Senior Notes	1,098		1,082		3,281		3,227
Amortization of LP Units and Certain Other Awards	4,304		4,866		13,513		13,577
Acquisition Related Compensation Charges	3,123		6,802		13,225		22,799
Special Charges	0		0		0		662
Intangible Asset Amortization	0		389		0		3,024
Total Investment Banking	7,427	[1]	12,057	[1]	26,738	[1]	40,062	[1]
Investment Management [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	(555)	[3]	(820)	[3]	(1,854)	[3]	(2,274)	[3]
Interest expense on Senior Notes	927		914		2,770		2,727
Amortization of LP Units and Certain Other Awards	511		596		1,693		1,696
Intangible Asset Amortization	82		82		246		246
Total Investment Management	$ 593	[1]	$ 678	[1]	$ 1,939	[1]	$ 1,942	[1]

[1] Other Expenses are as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2013 2012 2013 2012Investment Banking Amortization of LP Units and Certain Other Awards$4,304 $4,866 $13,513 $13,577Acquisition Related Compensation Charges3,123 6,802 13,225 22,799Special Charges— — — 662Intangible Asset Amortization— 389 — 3,024Total Investment Banking7,427 12,057 26,738 40,062Investment Management Amortization of LP Units and Certain Other Awards511 596 1,693 1,696Intangible Asset Amortization82 82 246 246Total Investment Management593 678 1,939 1,942Total Other Expenses$8,020 $12,735 $28,677 $42,004

[2] Investment Banking Other Revenue, net, includes interest expense on the Senior Notes of $1,098 and $3,281 for the three and nine months ended September 30, 2013, respectively, and $1,082 and $3,227 for the three and nine months ended September 30, 2012, respectively.

[3] Investment Management Other Revenue, net, includes interest expense on the Senior Notes of $927 and $2,770 for the three and nine months ended September 30, 2013, respectively, and $914 and $2,727 for the three and nine months ended September 30, 2012, respectively.