Organization and Basis of Presentation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012 Segment	Dec. 31, 2012 Class B Common stock [Member]	Dec. 31, 2011 Class B Common stock [Member]	Dec. 31, 2012 Class A Common stock [Member]	Dec. 31, 2011 Class A Common stock [Member]	Dec. 31, 2012 LAZ-MD Holdings LLC [Member]	Dec. 31, 2011 LAZ-MD Holdings LLC [Member]	Dec. 31, 2012 LAZ-MD Holdings LLC [Member] Class B Common stock [Member]	Dec. 31, 2011 LAZ-MD Holdings LLC [Member] Class B Common stock [Member]	Dec. 31, 2012 Lazard Ltd [Member]	Dec. 31, 2011 Lazard Ltd [Member]
Organization And Basis Of Presentation [Line Items]
Common membership interests held						98.80%	94.80%			1.20%	5.20%
Governing Operating Agreement, Date	May 10, 2005
Common membership voting power held								1.20%	5.20%
Common stock, par value		$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common stock, shares outstanding		1	1					1
Common stock, shares issued		1	1	128,216,423	123,009,311			1
Number of business segments	2