Incentive Plans - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended					3 Months Ended												3 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 RSUs [Member]	Mar. 31, 2013 Liability Awards [Member] RSUs [Member]	Dec. 31, 2012 Liability Awards [Member] RSUs [Member]	Mar. 01, 2013 Liability Awards [Member] RSUs [Member]	Mar. 31, 2014 Lazard Fund Interests [Member]	Mar. 31, 2014 Non-Executive [Member]	Mar. 31, 2014 DSUs [Member]	Mar. 31, 2013 DSUs [Member]	Mar. 31, 2014 RSUs [Member]	Mar. 31, 2014 Restricted Stock [Member]	Mar. 31, 2014 PRSUs [Member]	Mar. 31, 2013 PRSUs [Member] March 2015 [Member]	Mar. 31, 2013 PRSUs [Member] March 2016 [Member]	Mar. 31, 2014 Class A Common Stock [Member] RSUs [Member]	Mar. 31, 2013 Class A Common Stock [Member] RSUs [Member]	Mar. 31, 2014 Class A Common Stock [Member] 2005 Plan [Member]	Mar. 31, 2014 Class A Common Stock [Member] Awarded under 2008 Plan [Member]	Mar. 31, 2014 Class A Common Stock [Member] Restricted Stock [Member]	Mar. 31, 2013 Class A Common Stock [Member] Restricted Stock [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		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								0	0
Units granted under the directors deferred unit plan								2,310	1,886
Withholding taxes in lieu of share delivery															1,843,389	3,231,285			29,999	12,308
Delivery of common stock associated with stock awards															4,474,223	5,037,459			175,076	1,702,967
RSU's modified through a forward purchase agreements				958,213
Liability award					$ 28,612
Liability awards, compensation expense			1,690
Unrecognized compensation expense										$ 267,421	$ 20,657	$ 33,673
Unrecognized compensation expense, years						2 years 2 months 12 days				1 year 7 months 6 days	1 year 10 months 24 days	2 years
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 Share?Based?Compensation?Arrangement?By?Share?Based?Payment?Award?Award?Vesting?Period?1 P3Y												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)).