Condensed Statements Of Operations, Parent Company Only (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Revenues
TOTAL REVENUES									$ 657,674		$ 543,655		$ 398,746
Interest Expense									15,301		19,391		22,841
Net Revenues	214,049	153,029	172,497	102,798	112,781	163,181	141,204	107,098	642,373	[1]	524,264	[1]	375,905	[1]
EXPENSES
Total Expenses	171,811	138,784	151,302	114,941	113,790	149,739	129,589	95,334	576,838		488,452		339,045
Provision for Income Taxes	18,586	7,187	9,773	(4,638)	1,080	11,144	6,064	4,436	30,908		22,724		16,177
Net Income	24,985	7,473	12,141	(5,120)	(3,338)	1,293	5,259	7,317	39,479		10,531		17,805
Parent Company
Revenues
Interest Income									7,955		7,817		7,693
TOTAL REVENUES									7,955		7,817		7,693
Interest Expense									7,955		7,817		7,693
Net Revenues
EXPENSES
Total Expenses
OPERATING INCOME
Equity in Income of Subsidiary									53,229		21,083		20,618
Provision for Income Taxes									24,340		14,131		11,664
Net Income									$ 28,889		$ 6,952		$ 8,954

[1] Net revenues include Other Revenue, net, allocated to the segments as follows: For the Years Ended December 31, 2012 2011 2010 Investment Banking(A) $ (3,019 ) $ (2,473 ) $ (84 ) Investment Management(B) (2,636 ) (3,021 ) (552 ) Total Other Revenue, net $ (5,655 ) $ (5,494 ) $ (636 )