Senior and Subordinated Debt - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified				0 Months Ended		3 Months Ended			0 Months Ended	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 25, 2012	Nov. 30, 2013 7.125% Senior Notes [Member]	Nov. 30, 2013 Lazard Group 4.25% Senior Notes [Member]	Mar. 31, 2014 Lazard Group 4.25% Senior Notes [Member]	Mar. 31, 2014 LFB [Member]	Mar. 31, 2014 Edgewater [Member]	Mar. 31, 2014 Revolving Credit Facility [Member]	Mar. 31, 2014 Revolving Credit Facility [Member]	Mar. 31, 2014 Senior Debt [Member]	Dec. 31, 2013 Senior Debt [Member]
Debt Instrument [Line Items]
Redemption of senior debt				$ 528,500
Senior notes interest rate				7.125%	4.25%	4.25%
Senior Debt, Maturity Date				May 15, 2015	Nov. 14, 2020	Nov. 14, 2020
Senior Debt, Initial Principal Amount					500,000	500,000
Interest rate, payment terms					Interest on the 2020 Notes is payable semi-annually on May 14 and November 14 of each year commencing on May 14, 2014.
Senior revolving credit facility over next 3 years			150,000
Expiration date of credit facility										Sep. 25, 2015
Duration of senior revolving credit facility, in years			3 years
Revolving credit facility annual interest rate									0.78%
Outstanding credit facility	0	0
Unused lines of credit	258,000						48,000	55,000
Fair value of senior debt											1,140,000	1,117,000
Fair value of senior debt in excess of the aggregate carrying amount											$ 92,000	$ 69,000