Acquisition And Transition Costs And Intangible Asset Amortization (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Business Acquisition [Line Items]
Special Charges		$ 2,626	$ 662	$ 2,626
Special charges incurred in connection with exiting of a lease commitment for office space		731		731
Acquisition and Transition Costs		1,178	148	2,312
Lexicon Partnership LLP [Member]
Business Acquisition [Line Items]
Business combination acquisition related introduction fee		1,895		1,895
Investment Banking [Member]
Business Acquisition [Line Items]
Special Charges		2,626	662	2,626
Finite-lived intangible assets, amortization expense	593	2,208	3,636	3,558
Investment Management [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets, amortization expense	$ 1,674	$ 1,670	$ 5,023	$ 5,010