Investments - Company's Investments and Securities Sold, Not Yet Purchased (Parenthetical) (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule of Investments [Line Items]
Investments	$ 787,139	$ 1,007,339
Alternative Investment Funds [Member]
Schedule of Investments [Line Items]
Investments	54,003	49,757
Alternative Investment Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	23,799	18,326
Debt Funds [Member]
Schedule of Investments [Line Items]
Investments	181,322	164,952
Debt Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	150,882	132,875
Equity Funds [Member]
Schedule of Investments [Line Items]
Investments	352,544	375,761
Equity Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	$ 277,940	$ 306,618