Investments (Company's Investments And Securities Sold, Not Yet Purchased) (Details) (USD $) In Thousands	Jun. 30, 2011		Dec. 31, 2010
Total debt securities	$ 99,160		$ 95,544
Equities	110,634	[1]	88,437	[1]
Total Investments	435,139		417,410
Investments, at fair value	416,198		398,365
Interest-bearing deposits	7,660		7,754
Interests in LAM alternative asset management funds	39,360		58,656
Private equity	174,704		163,482
Equity method investments	11,281		11,291
Securities sold, not yet purchased, at fair value (included in "other liabilities")	1,262		2,897
Lazard Fund Interests Fixed Income Funds	2,051
Lazard Fund Interests Equities	23,051
U.S. Government And Agencies [Member] | Debt [Member]
Total debt securities	31,889		31,900
Fixed Income Funds [Member] | Debt [Member]
Total debt securities	40,403	[1]	33,951	[1]
Corporate And Other Debt And Interest-Bearing Deposits [Member] | Debt [Member]
Total debt securities	26,868		29,693
Other [Member]
Other investments	$ 225,345		$ 233,429

[1] At June 30, 2011 fixed income funds and equities include investments with fair values of $2,051 and $23,051, respectively, held in connection with previously granted Lazard Fund Interest awards ("Lazard Fund Interests"), which will serve to satisfy the Company's liability upon vesting. Lazard Fund Interests represent grants by the Company to eligible employees of actual or notional interests in several Lazard managed fixed income and equity investment funds (see Note 13 of Notes to Condensed Consolidated Financial Statements).