Goodwill and Other Intangible Assets - Estimated Future Amortization Expense (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2012
Intangible Assets [Line Items]
Intangible asset amortization attributable to noncontrolling interest, percentage	45.00%

Percentage of Intangible asset amortization attributable to noncontrolling interest

No definition available.

Name:	laz_IntangibleAssetAmortizationAttributableToNoncontrollingInterestPercentage
Namespace Prefix:	laz_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration