Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2017	Jun. 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	$ (4,815)	$ 7,090
Tax benefit related to delivery of Class A Common Stock		$ 11,126

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