Incentive Plans - Schedule of Issuance of RSUs and Charges to Retained Earnings (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of RSUs issued	288,272	257,418
Charges to retained earnings, net of estimated forfeitures	$ 13,489	$ 8,440

Charge To Retained Earnings Pertaining To Issuance Of Restricted Stock Units In Connection With Participation Rights

No definition available.

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