Delivery of common stock associated with stock awards.

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- Definition

Percentage Of Annual Compensation Received By Directors In Deferred Stock Units

+ References

No definition available.

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- Definition

Percentage of outstanding Class A common stock that may be awarded under the 2008 plan.

+ References

No definition available.

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- Definition

Percentage Of Target Number Of Shares Subject To Each PRSU No Longer Subject To Forfeiture Due To Threshold Level Of Performance Being Achieved.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award award vesting terms.

+ References

No definition available.

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- Definition

Share Based Compensation Arrangement By Share Based Payment Award Target Shares Earned Description

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No definition available.

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- Definition

Units Granted, Directors Deferred Unit Plan

+ References

No definition available.

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- Definition

Describe the conversion features of common stock if such stock is convertible. That is, shares of common stock into which another convertible security was converted, or shares of common stock into which another class of common stock was converted.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 6

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

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- Definition

Number of shares issued pursuant to the terms of a deferred compensation arrangement.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (l)

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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- Definition

Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

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- Definition

Percentage of vesting of share-based compensation awards.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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- Definition

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

+ References

No definition available.

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Incentive Plans - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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-MDInterests”). Following the Final Exchange of LAZ-MD Interests, Lazard Group became a wholly-owned indirect subsidiary of Lazard Ltd.
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%
PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 21,631
Unrecognized compensation expense, years	6 months
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 2015 and 2014 will vest on a single date three years following the date of the grant
Vesting period of PRSUs granted in 2015 and 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 generally can range from zero to two times the target number (with the exception of the PRSUs granted in 2013, for which (i) the performance period ended on December 31, 2014 and (ii) the number of shares of Class A common stock that may be received is equal to approximately 2.2 times the target number).
DSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual compensation paid in DSUs	23,961	26,360
Units granted under the directors deferred unit plan	1,761	6,381
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
Unrecognized compensation expense	$ 158,948
Unrecognized compensation expense, years	10 months 24 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 18,183
Unrecognized compensation expense, years	1 year
March 2015 [Member] \| PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period associated with PRSUs			33.00%
March 2016 [Member] \| PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period associated with PRSUs			67.00%
Class A Common Stock [Member] \| 2005 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
Class A Common Stock [Member] \| Awarded Under 2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of outstanding Class A common stock	30.00%
Class A Common Stock [Member] \| PRSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding taxes in lieu of share delivery	32,086
Delivery of common stock associated with stock awards	664,413
Class A Common Stock [Member] \| RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding taxes in lieu of share delivery	1,940,996	1,876,398
Delivery of common stock associated with stock awards	5,218,646	4,653,403
Class A Common Stock [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Withholding taxes in lieu of share delivery	94,745	29,999
Delivery of common stock associated with stock awards	417,771	175,076