Incentive Plans - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	9 Months Ended									3 Months Ended	9 Months Ended		9 Months Ended					9 Months Ended
	May 31, 2014	Sep. 30, 2014 Non-Executive [Member]	Sep. 30, 2014 Lazard Fund Interests [Member]	Sep. 30, 2014 RSUs [Member]	Sep. 30, 2014 DSUs [Member]	Sep. 30, 2013 DSUs [Member]	Sep. 30, 2014 Restricted Stock [Member]	Sep. 30, 2014 PRSUs [Member]	Sep. 30, 2013 PRSUs [Member] March 2015 [Member]	Sep. 30, 2013 PRSUs [Member] March 2016 [Member]	Dec. 31, 2012 Liability Awards [Member] RSUs [Member]	Sep. 30, 2013 Liability Awards [Member] RSUs [Member]	Mar. 01, 2013 Liability Awards [Member] RSUs [Member]	Sep. 30, 2014 Class A Common Stock [Member] RSUs [Member]	Sep. 30, 2013 Class A Common Stock [Member] RSUs [Member]	Sep. 30, 2014 Class A Common Stock [Member] Restricted Stock [Member]	Sep. 30, 2013 Class A Common Stock [Member] Restricted Stock [Member]	Sep. 30, 2014 Class A Common Stock [Member] 2005 Plan [Member]	Sep. 30, 2014 Class A Common Stock [Member] Awarded Under 2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized pertaining to share based compensation arrangements, 2005 Plan																		25,000,000
Percentage of outstanding Class A common stock																			30.00%
Common stock conversion basis	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.			One-for-one
Grant date fair value, amortized periods				Generally one-third after two years, and the remaining two-thirds after the third year
Percentage of annual compensation received by directors in the form of DSUs		55.00%
Annual compensation paid in DSUs					26,360	39,315
Units granted under the directors deferred unit plan					6,381	5,880
Withholding taxes in lieu of share delivery														1,876,398	3,471,813	29,999	18,631
Delivery of common stock associated with stock awards														4,653,403	5,891,979	175,076	1,709,878
RSUs' modified through a forward purchase agreements											958,213
Liability awards													$ 28,612
Liability awards, compensation expense												1,690
Unrecognized compensation expense				$ 168,382			$ 13,460	$ 23,850
Unrecognized compensation expense, years			1 year 8 months 12 days	1 year 1 month 6 days			1 year 4 months 24 days	1 year 7 months 6 days
Vesting period associated with PRSUs									33.00%	67.00%
Percentage of target number of shares subject to each PRSU no longer subject to forfeiture due to threshold level of performance being achieved								25.00%
Descriptions of vesting period associated with PRSUs								The PRSUs granted in 2014 will vest on a single date three years following the date of the grant
Vesting period of PRSUs granted in 2014								3 years
PSRU's target share distribution for Class A common stock, description								The target number of shares of Class A common stock subject to each PRSU is one; however, based on the achievement of the performance criteria, the number of shares of Class A common stock that may be received in connection with each PRSU can range from zero to two times the target number (or, for PRSUs granted in 2013, three times the target number in the event of a substantial increase in fiscal year 2014 revenue (adjusted for certain items)).