Segment Operating Results (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Segment Reporting Information [Line Items]
Total Other Revenue, net	$ 206		$ (885)		$ (2,456)		$ (2,820)
Special Charges	3,732		0		3,732		0
Acquisition and Transition Costs	4,122		0		5,238		58
Other Expenses	8,910	[1]	8,020	[1]	16,525	[1]	28,677	[1]
Investment Banking [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	850	[2]	(330)	[2]	(731)	[2]	(966)	[2]
Interest expense on Senior Notes	1,134		1,098		3,344		3,281
Amortization of LP Units and Certain Other Awards	0		4,304		0		13,513
Acquisition Related Compensation Charges	592		3,123		6,371		13,225
Special Charges	3,732		0		3,732		0
Intangible Asset Amortization	382		0		382		0
Professional Fees	0		0		1,672		0
Acquisition and Transition Costs	4,122		0		4,122		0
Other Expenses	8,828	[1]	7,427	[1]	16,279	[1]	26,738	[1]
Investment Management [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	(644)	[3]	(555)	[3]	(1,725)	[3]	(1,854)	[3]
Interest expense on Senior Notes	956		927		2,820		2,770
Amortization of LP Units and Certain Other Awards	0		511		0		1,693
Intangible Asset Amortization	82		82		246		246
Other Expenses	$ 82	[1]	$ 593	[1]	$ 246	[1]	$ 1,939	[1]

[1] Other Expenses are as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2014 2013 2014 2013Investment Banking Amortization of LP Units and Certain Other Awards$— $4,304 $— $13,513Acquisition Related Compensation Charges592 3,123 6,371 13,225Special Charges3,732 — 3,732 —Intangible Asset Amortization382 — 382 —Professional Fees— — 1,672 —Acquisition and Transition Costs4,122 — 4,122 —Total Investment Banking8,828 7,427 16,279 26,738Investment Management Amortization of LP Units and Certain Other Awards— 511 — 1,693Intangible Asset Amortization82 82 246 246Total Investment Management82 593 246 1,939Total Other Expenses$8,910 $8,020 $16,525 $28,677

[2] Investment Banking Other Revenue, net, includes interest expense on the Senior Notes of $1,134 and $3,344 for the three and nine months ended September 30, 2014, respectively, and $1,098 and $3,281 for the three and nine months ended September 30, 2013, respectively.

[3] Investment Management Other Revenue, net, includes interest expense on the Senior Notes of $956 and $2,820 for the three and nine months ended September 30, 2014, respectively, and $927 and $2,770 for the three and nine months ended September 30, 2013, respectively.