Investments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule Of Investments [Abstract]
Economic interests that are owned by management team and other investors in the Edgewater Funds	$ 9,286	$ 9,787

Economic interests that are owned by the management team and other investors.

No definition available.

Name:	laz_EconomicInterestsOwnedByManagementTeamAndOtherInvestors
Namespace Prefix:	laz_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant