Senior Debt - Senior Debt (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2015
Debt Instrument [Line Items]
Senior Debt, Outstanding Principal		$ 1,200,000,000	$ 998,350,000
Senior Debt, Outstanding Unamortized Debt Costs		11,400,000	8,992,000
Senior Debt, Outstanding Carrying Value		1,188,600,000	989,358,000
Lazard Group 6.85% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount			$ 600,000,000
Senior Debt, Maturity Date	Jun. 15, 2017		Jun. 15, 2017
Senior Debt, Annual Interest Rate	6.85%		6.85%
Senior Debt, Outstanding Principal			$ 98,350,000
Senior Debt, Outstanding Unamortized Debt Costs			159,000
Senior Debt, Outstanding Carrying Value			98,191,000
Lazard Group 4.25% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount		$ 500,000,000
Senior Debt, Maturity Date		Nov. 14, 2020
Senior Debt, Annual Interest Rate		4.25%
Senior Debt, Outstanding Principal		$ 500,000,000	500,000,000
Senior Debt, Outstanding Unamortized Debt Costs		3,569,000	4,491,000
Senior Debt, Outstanding Carrying Value		496,431,000	495,509,000
Lazard Group 3.75% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount		$ 400,000,000		$ 400,000,000
Senior Debt, Maturity Date		Feb. 13, 2025
Senior Debt, Annual Interest Rate		3.75%		3.75%
Senior Debt, Outstanding Principal		$ 400,000,000	400,000,000
Senior Debt, Outstanding Unamortized Debt Costs		3,833,000	4,342,000
Senior Debt, Outstanding Carrying Value		396,167,000	$ 395,658,000
Lazard Group 3.625% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount	$ 300,000,000	$ 300,000,000
Senior Debt, Maturity Date		Mar. 01, 2027
Senior Debt, Annual Interest Rate	3.625%	3.625%
Senior Debt, Outstanding Principal		$ 300,000,000
Senior Debt, Outstanding Unamortized Debt Costs		3,998,000
Senior Debt, Outstanding Carrying Value		$ 296,002,000