Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Statement Of Stockholders Equity [Abstract]
Tax expense related to delivery of Class A Common Stock in connection with share-based incentive compensation	$ 7,512	$ 4,815

Tax expense (benefit) from stock issued in connection with share-based incentive compensation.

No definition available.

Name:	laz_TaxExpenseBenefitFromStockIssuedInConnectionWithSharebasedIncentiveCompensation
Namespace Prefix:	laz_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration