Senior Debt - Senior Debt (Parenthetical) (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2015
Debt Instrument [Line Items]
Loss on extinguishment of debt		$ 3,148,000	$ 60,219,000
Lazard Group 3.625% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount	$ 300,000,000	$ 300,000,000
Senior notes interest rate	3.625%	3.625%
Original Maturity Date		Mar. 01, 2027
Interest rate, payment terms		Interest on the 2027 Notes is payable semi-annually on March 1 and September 1 of each year, beginning March 1, 2017.
Effective interest rates of senior notes		3.76%
Lazard Group 6.85% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount			$ 600,000,000
Senior notes interest rate	6.85%		6.85%
Redemption of senior debt	$ 98,350,000
Original Maturity Date	Jun. 15, 2017		Jun. 15, 2017
Loss on extinguishment of debt		$ 3,148,000	$ 60,219,000
Lazard Group 3.75% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount		$ 400,000,000		$ 400,000,000
Senior notes interest rate		3.75%		3.75%
Original Maturity Date		Feb. 13, 2025
Interest rate, payment terms		Interest on the 2025 Notes is payable semi-annually on March 1 and September 1 of each year.
Effective interest rates of senior notes		3.87%
Lazard Group 4.25% Senior Notes [Member]
Debt Instrument [Line Items]
Senior Debt, Initial Principal Amount		$ 500,000,000
Senior notes interest rate		4.25%
Original Maturity Date		Nov. 14, 2020
Effective interest rates of senior notes		4.43%