Segment Operating Results (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		Dec. 31, 2012
Segment Reporting Information [Line Items]
Net Revenues	$ 187,328	[1]	$ 153,029	[1]	$ 546,756	[1]	$ 428,324	[1]
Operating Expenses	147,440		126,049		431,780		363,023
Other Expenses	8,020	[2]	12,735	[2]	28,677	[2]	42,004	[2]
Operating Income (Loss)	31,868		14,245		86,299		23,297
Income (Loss) from Equity Method Investments	562		415		2,333		3,519
Pre-Tax Income (Loss) from Continuing Operations	32,430		14,660		88,632		26,816
Identifiable Segment Assets	1,103,341		1,028,764		1,103,341		1,028,764		1,145,218
Investment Banking [Member]
Segment Reporting Information [Line Items]
Net Revenues	163,645	[1]	133,415	[1]	477,846	[1]	370,364	[1]
Operating Expenses	126,472		106,897		369,927		304,556
Other Expenses	7,427	[2]	12,057	[2]	26,738	[2]	40,062	[2]
Operating Income (Loss)	29,746		14,461		81,181		25,746
Income (Loss) from Equity Method Investments	0		(200)		460		1,395
Pre-Tax Income (Loss) from Continuing Operations	29,746		14,261		81,641		27,141
Identifiable Segment Assets	611,266		519,000		611,266		519,000
Investment Management [Member]
Segment Reporting Information [Line Items]
Net Revenues	23,683	[1]	19,614	[1]	68,910	[1]	57,960	[1]
Operating Expenses	20,968		19,152		61,853		58,467
Other Expenses	593	[2]	678	[2]	1,939	[2]	1,942	[2]
Operating Income (Loss)	2,122		(216)		5,118		(2,449)
Income (Loss) from Equity Method Investments	562		615		1,873		2,124
Pre-Tax Income (Loss) from Continuing Operations	2,684		399		6,991		(325)
Identifiable Segment Assets	$ 492,075		$ 509,764		$ 492,075		$ 509,764

[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, 2013 2012 2013 2012Investment Banking (A)$(330) $(435) $(966) $(2,407)Investment Management (B)(555) (820) (1,854) (2,274)Total Other Revenue, net$(885) $(1,255) $(2,820) $(4,681) (A)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.(B)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.

[2] 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