Organization and Basis of Presentation - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended												12 Months Ended
	May 31, 2014	Sep. 30, 2014 Segment	Dec. 31, 2013 Class B Common Stock [Member]	Sep. 30, 2013 Class B Common Stock [Member]	Dec. 31, 2012 Class B Common Stock [Member]	Sep. 30, 2014 Class A Common Stock [Member]	May 31, 2014 Class A Common Stock [Member]	Dec. 31, 2013 Class A Common Stock [Member]	Sep. 30, 2013 Class A Common Stock [Member]	Dec. 31, 2012 Class A Common Stock [Member]	Sep. 30, 2014 Lazard Ltd [Member]	Dec. 31, 2013 Lazard Ltd [Member]	Dec. 31, 2013 LAZ-MD Holdings LLC [Member]	Dec. 31, 2013 LAZ-MD Holdings LLC [Member] Class B Common Stock [Member]
Organization And Basis Of Presentation [Line Items]
Percentage of common membership interests held											100.00%	99.50%	0.50%
Governing operating agreement, date		May 10, 2005
Common membership voting power held														0.60%
Common stock, par value			$ 0.01			$ 0.01	$ 0.01	$ 0.01
Common stock, shares outstanding			1			129,766,091		129,056,081						1
Common stock, shares issued			1	1	1	129,766,091		129,056,081	129,056,081	128,216,423				1
Common stock, Class B shares conversion to Class A shares	1
Common stock conversion	In May 2014, the remaining outstanding Lazard Group common membership interests held by LAZ-MD Holdings were exchanged for shares of the Company’s Class A common stock, and the sole issued and outstanding share of the Company’s Class B common stock was automatically converted into one share of the Company’s Class A common stock pursuant to the provisions of the Company’s bye-laws, resulting in only one outstanding class of common stock (the “Final Exchange of LAZ-MD Interests”). Following the Final Exchange of LAZ-MD Interests, Lazard Group became a wholly-owned indirect subsidiary of Lazard Ltd.
Number of business segments		2
Short-term investments maturity days		Original maturities of 90 days or less