Incentive Plans - Additional Information (Detail) - USD ($) $ in Thousands			6 Months Ended
	Apr. 29, 2021	Apr. 24, 2018	Jun. 30, 2021
Lazard Fund Interests [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, years			10 months 24 days
Non-Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of annual compensation received by directors in the form of DSUs			55.00%
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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
Number of dividend participation rights issued			220,811
Charges to retained earnings, net of estimated forfeitures			$ 9,132
Unrecognized compensation expense			$ 142,097
Unrecognized compensation expense, years			10 months 24 days
DSUs [Member] | Non-Executive [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual compensation received for service			30,764
Units granted under the directors deferred unit plan			8,317
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Charges to retained earnings, net of estimated forfeitures			$ 831
Unrecognized compensation expense			$ 22,309
Unrecognized compensation expense, years			10 months 24 days
Dividend participation rights issued			19,202
PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense			$ 1,662
Unrecognized compensation expense, years			1 year 4 months 24 days
Descriptions of vesting period			PRSUs will vest on a single date approximately three years following the date of the grant
Vesting period			3 years
PRSUs target share distribution for Class A common stock, description			The target number of shares of common stock subject to each PRSU is one; however, based on the achievement of the performance criteria, the number of shares of common stock that may be received in connection with each PRSU generally can range from zero to two times the target number for awards granted prior to February 2021. For awards granted in February 2021, based on both the performance-based and market-based criteria, the number of shares of common stock can range from zero to 2.4 times the target number.
Profits Interest Participation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock conversion basis			one-for-one
Unrecognized compensation expense			$ 46,902
Unrecognized compensation expense, years			8 months 12 days
Descriptions of vesting period			Profits interest participation rights generally provide for vesting approximately three years following the grant date
Vesting period			3 years
PRSUs target share distribution for Class A common stock, description			The target number of shares of common stock subject to each PRPU is one. Based on the achievement of performance criteria, as determined by the Compensation Committee, the number of shares of common stock that may be received in connection with the PRPU awards granted in February 2019 and February 2020 will range from zero to two times the target number. For the PRPU awards granted in February 2021, subject to both performance-based and incremental market-based criteria, the number of shares will range from zero to 2.4 times the target number.
Percentage of target number of shares subject to the applicable units no longer subject to forfeiture due to threshold level of performance being achieved			25.00%
Common Stock [Member] | RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding taxes in lieu of share delivery			1,352,483
Delivery of common stock associated with stock awards			2,382,906
Common Stock [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding taxes in lieu of share delivery			175,849
Delivery of common stock associated with stock awards			326,028
Common Stock [Member] | PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding taxes in lieu of share delivery			100,882
Delivery of common stock associated with stock awards			446,077
Common Stock [Member] | 2018 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized pertaining to share based compensation arrangements		30,000,000
Share-based compensation arrangement by share-based payment award, number of additional shares authorized	20,000,000
Common Stock [Member] | Awarded Under 2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of outstanding common stock available under the plan		30.00%
Compensation plan expiration period		Apr. 24, 2018
Common Stock [Member] | 2005 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized pertaining to share based compensation arrangements			25,000,000