Investments - Schedule of Equity Securities and Trading Debt Securities Net Unrealized Investment Gains and Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Realized Or Unrealized Gain Loss On Trading Securities [Abstract]
Net unrealized investment gains	$ 14,154	$ 49,719	$ 36,610

Amount of unrealized gain (loss) on investment in debt and equity security measured at fair value with change in fair value recognized in net income (trading).

No definition available.

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