Segment Operating Results (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Segment Reporting Information [Line Items]
Total Other Revenue, net	$ (1,746)		$ (1,965)		$ (3,246)		$ (3,426)
Special Charges	0		662		0		662
Total Other Expenses	10,052	[1]	12,554	[1]	20,657	[1]	29,269	[1]
Investment Banking [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	(849)	[2]	(1,262)	[2]	(636)	[2]	(1,972)	[2]
Interest expense on Senior Notes	1,095		1,075		2,183		2,145
Amortization of LP Units and Certain Other Awards	4,300		4,495		9,209		8,711
Acquisition Related Compensation Charges	5,156		6,352		10,102		15,997
Special Charges	0		662		0		662
Intangible Asset Amortization	0		389		0		2,635
Total Investment Banking	9,456	[1]	11,898	[1]	19,311	[1]	28,005	[1]
Investment Management [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	(897)	[3]	(703)	[3]	(2,610)	[3]	(1,454)	[3]
Interest expense on Senior Notes	924		909		1,843		1,813
Amortization of LP Units and Certain Other Awards	514		574		1,182		1,100
Intangible Asset Amortization	82		82		164		164
Total Investment Management	$ 596	[1]	$ 656	[1]	$ 1,346	[1]	$ 1,264	[1]

[1] Other Expenses are as follows: For the Three Months Ended June 30, For the Six Months Ended June 30, 2013 2012 2013 2012Investment Banking Amortization of LP Units and Certain Other Awards$4,300 $4,495 $9,209 $8,711Acquisition Related Compensation Charges5,156 6,352 10,102 15,997Special Charges— 662 — 662Intangible Asset Amortization— 389 — 2,635Total Investment Banking9,456 11,898 19,311 28,005Investment Management Amortization of LP Units and Certain Other Awards514 574 1,182 1,100Intangible Asset Amortization82 82 164 164Total Investment Management596 656 1,346 1,264Total Other Expenses$10,052 $12,554 $20,657 $29,269

[2] Investment Banking Other Revenue, net, includes interest expense on the Senior Notes of $1,095 and $2,183 for the three and six months ended June 30, 2013, respectively, and $1,075 and $2,145 for the three and six months ended June 30, 2012, respectively.

[3] Investment Management Other Revenue, net, includes interest expense on the Senior Notes of $924 and $1,843 for the three and six months ended June 30, 2013, respectively, and $909 and $1,813 for the three and six months ended June 30, 2012, respectively.