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 $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd	$ 60,282	$ 33,301	$ 106,995	$ 89,674
Add - adjustment associated with Class A common stock issuable on a non-contingent basis		3		6
Net income attributable to Lazard Ltd - basic	60,282	33,304	106,995	89,680
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 and exchangeable interests, net of tax	316	1,804	787	4,680
Net income attributable to Lazard Ltd - diluted	$ 60,598	$ 35,108	$ 107,782	$ 94,360
Weighted average number of shares of Class A common stock outstanding	121,441,956	114,689,712	119,797,545	116,949,317
Add - adjustment for shares of Class A common stock issuable on a non-contingent basis	757,998	913,639	758,502	740,087
Weighted average number of shares of Class A common stock outstanding - basic	122,199,954	115,603,351	120,556,047	117,689,404
Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation and exchangeable interests	12,042,190	19,776,685	12,617,953	17,847,646
Weighted average number of shares of Class A common stock outstanding - diluted	134,242,144	135,380,036	133,174,000	135,537,050
Net income attributable to Lazard Ltd per share of Class A common stock:
Basic	$ 0.49	$ 0.29	$ 0.89	$ 0.76
Diluted	$ 0.45	$ 0.26	$ 0.81	$ 0.70