Schedule I - Condensed Statements of Comprehensive Income (Parent Company Only) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
NET INCOME	$ 127,982	$ 112,536	$ 80,357	$ 66,823	$ 157,786	$ 398,521	$ 374,113	$ 55,953	$ 387,698	$ 986,373	$ 427,277
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Currency translation adjustments									(57,920)	(51,182)	(49,971)
Employee benefit plans:
Actuarial gain (loss) (net of tax expense (benefit) of $(5,205), $5,644 and $(9,045) for the years ended December 31, 2016, 2015 and 2014, respectively)									(24,473)	11,283	(21,983)
Adjustment for items reclassified to earnings (net of tax expense of $1,757, $1,507 and $1,923 for the years ended December 31, 2016, 2015, and 2014, respectively)									2,526	6,309	4,749
OTHER COMPREHENSIVE LOSS, NET OF TAX									(79,867)	(33,590)	(67,205)
COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD									307,832	952,783	360,073
Parent Company [Member]
NET INCOME									387,698	986,373	427,277
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Currency translation adjustments									(57,919)	(51,182)	(49,970)
Employee benefit plans:
Actuarial gain (loss) (net of tax expense (benefit) of $(5,205), $5,644 and $(9,045) for the years ended December 31, 2016, 2015 and 2014, respectively)									(24,473)	11,283	(21,983)
Adjustment for items reclassified to earnings (net of tax expense of $1,757, $1,507 and $1,923 for the years ended December 31, 2016, 2015, and 2014, respectively)									2,526	6,309	4,749
OTHER COMPREHENSIVE LOSS, NET OF TAX									(79,866)	(33,590)	(67,204)
COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD									$ 307,832	$ 952,783	$ 360,073