Acquisitions - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Sep. 01, 2015	Aug. 04, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Payments of contingent consideration obligation			$ 2,166	$ 1,000	$ 0
Purchase price allocated to goodwill			3,829	$ 2,570	$ 0
Contingent consideration payable			$ 1,267
Lazard Capital Markets LLC [Member]
Business Acquisition [Line Items]
Completed date of purchase of LCM's securities lending business			Aug. 04, 2014
Payments of contingent consideration obligation		$ 1,000	$ 2,166
Purchase price allocated to goodwill		2,570
Purchase price allocated to intangible assets		2,500
Transaction costs related to acquisition		379
Contingent consideration payable		$ 4,070
Contingent on performance of business		18 years
Decrease in aggregate remaining contingent payment			637
Business combination contingent consideration liability, remaining amount			$ 1,267
Lazard Capital Markets LLC [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Purchase price allocated to intangible assets		$ 2,500
MLV [Member]
Business Acquisition [Line Items]
Payments of contingent consideration obligation	$ 3,250
Percentage of voting interest acquired	100.00%
Purchase price allocated to goodwill	$ 1,259
Purchase price allocated to intangible assets	506
Transaction costs related to acquisition	$ 691