Senior Debt - Senior Debt (Parenthetical) (Detail)	3 Months Ended
Mar. 31, 2018
Lazard Group 4.25% Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes interest rate	4.25%
Original Maturity Date	Nov. 14, 2020
Effective interest rates of senior notes	4.43%
Lazard Group 3.75% Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes interest rate	3.75%
Original Maturity Date	Feb. 13, 2025
Effective interest rates of senior notes	3.87%
Lazard Group 3.625% Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes interest rate	3.625%
Original Maturity Date	Mar. 01, 2027
Effective interest rates of senior notes	3.76%

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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