Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Statement Of Stockholders Equity [Abstract]
Tax (expense) benefit related to delivery of Class A Common Stock in connection with share-based incentive compensation	$ (4,819)	$ 6,900
Tax benefit related to delivery of Class A Common Stock	$ 832	$ 12,653

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

No definition available.

Name:	laz_TaxBenefitExpenseFromStockIssuedInConnectionWithSharebasedIncentiveCompensation
Namespace Prefix:	laz_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration