Investments - Company's Investments and Securities Sold, Not Yet Purchased (Parenthetical) (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Investments	$ 869,844	$ 1,007,339
Alternative Investment Funds [Member]
Schedule of Investments [Line Items]
Investments	55,390	49,757
Alternative Investment Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	24,201	18,326
Debt Funds [Member]
Schedule of Investments [Line Items]
Investments	195,767	164,952
Debt Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	164,500	132,875
Equity Funds [Member]
Schedule of Investments [Line Items]
Investments	400,586	375,761
Equity Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	$ 333,535	$ 306,618