Net Income Per Share of Class A 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, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd - basic	$ 107,553	$ 66,823
Net income attributable to Lazard Ltd - diluted	$ 107,553	$ 66,823
Weighted average number of shares of Class A common stock outstanding	122,531,221	125,968,430
Add - adjustment for shares of Class A common stock issuable on a non-contingent basis	283,942	72,011
Weighted average number of shares of Class A common stock outstanding - basic	122,815,163	126,040,441
Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation	9,874,212	6,850,843
Weighted average number of shares of Class A common stock outstanding - diluted	132,689,375	132,891,284
Net income attributable to Lazard Ltd per share of Class A common stock:
Basic	$ 0.88	$ 0.53
Diluted	$ 0.81	$ 0.50