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								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd - basic									$ 387,698	$ 986,373	$ 427,277
Adjustments to net income relating to interest expense and changes to net income attributable to noncontrolling interests resulting from assumed Class A common stock issuances in connection with share-based incentive compensation, and, in 2014, exchangable interests, net of tax											581
Net income attributable to Lazard Ltd - diluted									$ 387,698	$ 986,373	$ 427,858
Weighted average number of shares of Class A common stock outstanding									124,635,160	125,294,261	121,942,939
Add - adjustment for shares of Class A common stock issuable on a non-contingent basis									135,241	72,011	408,897
Weighted average number of shares of Class A common stock outstanding - basic									124,770,401	125,366,272	122,351,836
Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation and in 2014, exchangable interests									7,863,229	7,878,274	11,461,287
Weighted average number of shares of Class A common stock outstanding - diluted									132,633,630	133,244,546	133,813,123
Net income attributable to Lazard Ltd per share of Class A common stock:
Basic	$ 1.04	$ 0.90	$ 0.64	$ 0.53	$ 1.26	$ 3.16	$ 2.96	$ 0.45	$ 3.11	$ 7.87	$ 3.49
Diluted	$ 0.96	$ 0.85	$ 0.61	$ 0.50	$ 1.18	$ 2.99	$ 2.82	$ 0.42	$ 2.92	$ 7.40	$ 3.20