Segment Operating Results (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		Dec. 31, 2013
Segment Reporting Information [Line Items]
Net Revenues	$ 227,161	[1]	$ 187,328	[1]	$ 593,970	[1]	$ 546,756	[1]
Operating Expenses	178,905		147,440		474,350		431,780
Other Expenses	8,910	[2]	8,020	[2]	16,525	[2]	28,677	[2]
Operating Income	39,346		31,868		103,095		86,299
Income (Loss) from Equity Method Investments	1,102		562		3,381		2,333
Pre-Tax Income from Continuing Operations	40,448		32,430		106,476		88,632
Identifiable Segment Assets	1,223,751		1,103,341		1,223,751		1,103,341		1,180,783
Investment Banking [Member]
Segment Reporting Information [Line Items]
Net Revenues	203,028	[1]	163,645	[1]	522,202	[1]	477,846	[1]
Operating Expenses	156,549		126,472		410,832		369,927
Other Expenses	8,828	[2]	7,427	[2]	16,279	[2]	26,738	[2]
Operating Income	37,651		29,746		95,091		81,181
Income (Loss) from Equity Method Investments	(48)		0		455		460
Pre-Tax Income from Continuing Operations	37,603		29,746		95,546		81,641
Identifiable Segment Assets	719,351		611,266		719,351		611,266
Investment Management [Member]
Segment Reporting Information [Line Items]
Net Revenues	24,133	[1]	23,683	[1]	71,768	[1]	68,910	[1]
Operating Expenses	22,356		20,968		63,518		61,853
Other Expenses	82	[2]	593	[2]	246	[2]	1,939	[2]
Operating Income	1,695		2,122		8,004		5,118
Income (Loss) from Equity Method Investments	1,150		562		2,926		1,873
Pre-Tax Income from Continuing Operations	2,845		2,684		10,930		6,991
Identifiable Segment Assets	$ 504,400		$ 492,075		$ 504,400		$ 492,075

[1] Net revenues include Other Revenue, net, allocated to the segments as follows: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2014 2013 2014 2013Investment Banking (A)$850 $(330) $(731) $(966)Investment Management (B)(644) (555) (1,725) (1,854)Total Other Revenue, net$206 $(885) $(2,456) $(2,820) (A)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.(B)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.

[2] 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