Acquisition and Transition Costs and Intangible Asset Amortization (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	Aug. 03, 2014
Business Acquisition [Line Items]
Acquisition and Transition Costs	$ 4,122	$ 0	$ 5,238	$ 58
Special Charges	3,732	0	3,732	0
Business Acquisition, Percentage of Voting Interests Acquired	100.00%		100.00%
Payments to Acquire Businesses, Gross	6,900
Grant Of LP Units (in units)	72
Business Acquisitions Contingent Consideration Potential Cash Payment	3,391		3,391		11,086
Goodwill, Acquired During Period	3,401
Investment Banking [Member]
Business Acquisition [Line Items]
Acquisition and Transition Costs	4,122	0	4,122	0
Special Charges	3,732	0	3,732	0
Amortization of Intangible Assets	477	204	718	612
Investment Management [Member]
Business Acquisition [Line Items]
Amortization of Intangible Assets	940	1,793	4,190	4,775
Advisory Backlog [Member] | Investment Banking [Member]
Business Acquisition [Line Items]
Intangible Assets	2,450		2,450
Client Related Intangible Assets [Member] | Investment Banking [Member]
Business Acquisition [Line Items]
Intangible Assets	1,050		1,050
Intangible Assets Acquired [Member] | Investment Banking [Member]
Business Acquisition [Line Items]
Amortization of Intangible Assets	$ 382