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, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd - basic	$ 66,823	$ 55,953
Adjustments to income relating to interest expense and changes in net income attributable to noncontrolling interests resulting from assumed Class A common stock issuances in connection with share-based incentive compensation, net of tax	0	0
Net income attributable to Lazard Ltd - diluted	$ 66,823	$ 55,953
Weighted average number of shares of Class A common stock outstanding	125,968,430	123,583,678
Add - adjustment for shares of Class A common stock issuable on a non-contingent basis	72,011	72,011
Weighted average number of shares of Class A common stock outstanding - basic	126,040,441	123,655,689
Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation	6,850,843	10,080,257
Weighted average number of shares of Class A common stock outstanding - diluted	132,891,284	133,735,946
Net income attributable to Lazard Ltd per share of Class A common stock:
Basic	$ 0.53	$ 0.45
Diluted	$ 0.50	$ 0.42