Investments - Schedule of Equity Securities and Trading Debt Securities Net Unrealized Investment Gains and Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Net Realized Or Unrealized Gain Loss On Trading Securities [Abstract]
Net unrealized investment gains (losses)	$ (40,867)	$ 1,054

Amount of net unrealized gain (loss) on investments in equity securities and trading debt securities.

No definition available.

Name:	laz_NetUnrealizedGainsLossesOnInvestmentsInEquitySecuritiesAndTradingDebtSecurities
Namespace Prefix:	laz_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration