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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd - basic	$ 120,378	$ 80,357	$ 227,931	$ 147,180
Net income attributable to Lazard Ltd - diluted	$ 120,378	$ 80,357	$ 227,931	$ 147,180
Weighted average number of shares of Class A common stock outstanding	122,085,842	125,389,937	122,308,531	125,679,184
Add - adjustment for shares of Class A common stock issuable on a non-contingent basis	282,308	72,011	283,125	72,011
Weighted average number of shares of Class A common stock outstanding - basic	122,368,150	125,461,948	122,591,656	125,751,195
Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation	9,771,466	6,879,574	9,822,840	6,865,208
Weighted average number of shares of Class A common stock outstanding - diluted	132,139,616	132,341,522	132,414,496	132,616,403
Net income attributable to Lazard Ltd per share of Class A common stock:
Basic	$ 0.98	$ 0.64	$ 1.86	$ 1.17
Diluted	$ 0.91	$ 0.61	$ 1.72	$ 1.11