Schedule I - Condensed Statements of Comprehensive Income (Parent Company) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
NET INCOME	$ (4,106)	$ 33,673	$ 34,162	$ 29,056	$ (8,123)	$ 67,133	$ 71,566	$ 59,983	$ 92,785	$ 190,559	$ 194,423
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Currency translation adjustments									15,686	(9,474)	(9,457)
Amortization of interest rate hedge									1,055	1,054	1,163
Available-for-sale securities:
Unrealized gain (net of tax expense of $1,546)											3,129
Adjustments for items reclassified to earnings (net of tax expense of $4,689)											9,501
Employee benefit plans:
Actuarial gain (loss) (net of tax expense (benefit) of $(12,796), $(11,874) and $6,161 for the years ended December 31, 2012, 2011 and 2010, respectively)									(40,298)	(38,248)	17,841
Adjustments for items reclassified to earnings (net of tax expense of $1,131, $977 and $916 for the years ended December 31, 2012, 2011 and 2010, respectively)									4,399	2,206	1,643
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX									(19,158)	(44,462)	23,820
COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD									65,312	132,992	197,319
LAZARD LTD (parent company only) [Member]
NET INCOME									84,309	174,917	174,979
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Currency translation adjustments									15,431	(8,760)	(8,937)
Amortization of interest rate hedge									1,042	1,000	1,093
Available-for-sale securities:
Unrealized gain (net of tax expense of $1,546)											2,941
Adjustments for items reclassified to earnings (net of tax expense of $4,689)											8,930
Employee benefit plans:
Actuarial gain (loss) (net of tax expense (benefit) of $(12,796), $(11,874) and $6,161 for the years ended December 31, 2012, 2011 and 2010, respectively)									(39,817)	(36,256)	16,769
Adjustments for items reclassified to earnings (net of tax expense of $1,131, $977 and $916 for the years ended December 31, 2012, 2011 and 2010, respectively)									4,347	2,091	1,544
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX									(18,997)	(41,925)	22,340
COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD									$ 65,312	$ 132,992	$ 197,319