Net Income Per Share of Common Stock - Company's Basic and Diluted Net Income Per Share and Weighted Average Shares Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd	$ 87,300	$ 64,022
Add - adjustment for earnings attributable to participating securities	(1,292)	(1,013)
Net income attributable to Lazard Ltd - basic	86,008	63,009
Add - adjustment for earnings attributable to participating securities	1,292	1,013
Net income attributable to Lazard Ltd - diluted	$ 87,300	$ 64,022
Weighted average number of shares of common stock outstanding	105,545,273	104,462,177
Add - adjustment for shares of common stock issuable on a non-contingent basis	1,746,287	1,841,785
Weighted average number of shares of common stock outstanding - basic	107,291,560	106,303,962
Weighted average number of incremental shares of common stock issuable from share-based incentive compensation	8,530,734	7,816,217
Weighted average number of shares of common stock outstanding - diluted	115,822,294	114,120,179
Net income attributable to Lazard Ltd per share of common stock:
Basic	$ 0.80	$ 0.59
Diluted	$ 0.75	$ 0.56