Schedule I - Basis of Presentation (Parent Company Only) (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Organization And Basis Of Presentation [Line Items]
Gain on acquisition of portion of business already owned	$ 12,668
Parent Company [Member]
Organization And Basis Of Presentation [Line Items]
Gain on acquisition of portion of business already owned	$ 12,668

Amount of gain (loss) on acquisition of portion of business already owned.

No definition available.

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