Intangible Assets Associated with Acquisitions (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	$ 55,399	$ 66,610
Intangible assets, Accumulated Amortization	20,002	25,701
Client Related
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	49,260	61,085
Intangible assets, Accumulated Amortization	17,381	24,071
Acquired Mandates
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	1,810	1,810
Intangible assets, Accumulated Amortization	1,324	836
Non-Compete/Non-Solicit Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	2,084	1,915
Intangible assets, Accumulated Amortization	987	604
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	2,245	1,800
Intangible assets, Accumulated Amortization	310	190
Investment Banking
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	4,245	19,780
Intangible assets, Accumulated Amortization	2,360	14,750
Investment Banking | Client Related
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	2,300	17,835
Intangible assets, Accumulated Amortization	969	13,874
Investment Banking | Acquired Mandates
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	1,810	1,810
Intangible assets, Accumulated Amortization	1,324	836
Investment Banking | Non-Compete/Non-Solicit Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	135	135
Intangible assets, Accumulated Amortization	67	40
Investment Management
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	51,154	46,830
Intangible assets, Accumulated Amortization	17,642	10,951
Investment Management | Client Related
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	46,960	43,250
Intangible assets, Accumulated Amortization	16,412	10,197
Investment Management | Non-Compete/Non-Solicit Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	1,949	1,780
Intangible assets, Accumulated Amortization	920	564
Investment Management | Other
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, Gross Carrying Amount	2,245	1,800
Intangible assets, Accumulated Amortization	$ 310	$ 190