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
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share [Abstract]
Net income attributable to Lazard Ltd	$ 80,842	$ 15,360
Add (deduct) - adjustment associated with Class A common stock issuable on a non-contingent basis
Net income attributable to Lazard Ltd - basic	80,842	15,360
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	433	182
Net income attributable to Lazard Ltd - diluted	$ 81,275	$ 15,542
Weighted average number of shares of Class A common stock outstanding	121,361,210	116,921,983
Add - adjustment for shares of Class A common stock issuable on a non-contingent basis	414,997	786,221
Weighted average number of shares of Class A common stock outstanding - basic	121,776,207	117,708,204
Weighted average number of incremental shares of Class A common stock issuable from share-based incentive compensation and exchangeable interests	12,249,784	15,107,356
Weighted average number of shares of Class A common stock outstanding - diluted	134,025,991	132,815,560
Net income attributable to Lazard Ltd per share of Class A common stock:
Basic	$ 0.66	$ 0.13
Diluted	$ 0.61	$ 0.12