Investments - Company's Investments and Securities Sold, Not Yet Purchased (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Investments	$ 1,007,339	$ 658,532
Alternative Investment Funds [Member]
Schedule of Investments [Line Items]
Investments	49,757	34,264
Alternative Investment Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	18,326	11,128
Debt Funds [Member]
Schedule of Investments [Line Items]
Investments	164,952	123,554
Debt Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	132,875	90,758
Equity Funds [Member]
Schedule of Investments [Line Items]
Investments	375,761	325,795
Equity Funds [Member] | Lazard Fund Interests [Member]
Schedule of Investments [Line Items]
Investments	$ 306,618	$ 277,725