Schedule I - Condensed Statements of Comprehensive Income (Parent Company Only) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
NET INCOME	$ 172,805	$ 89,920	$ 85,909	$ 85,429	$ 52,796	$ 62,748	$ 31,921	$ 17,649	$ 434,063	$ 165,114	$ 92,785
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Currency translation adjustments									(49,971)	(15,536)	15,686
Amortization of interest rate hedge										2,502	1,055
Employee benefit plans:
Actuarial loss, net of tax benefit									(21,983)	(13,500)	(40,298)
Adjustments for items reclassified to earnings, net of tax expense									4,749	4,605	4,399
OTHER COMPREHENSIVE LOSS, NET OF TAX									(67,205)	(21,929)	(19,158)
COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD									360,073	138,416	65,312
Parent Company [Member]
NET INCOME									427,277	160,212	84,309
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX:
Currency translation adjustments									(49,970)	(15,438)	15,431
Amortization of interest rate hedge										2,488	1,042
Employee benefit plans:
Actuarial loss, net of tax benefit									(21,983)	(13,426)	(39,817)
Adjustments for items reclassified to earnings, net of tax expense									4,749	4,580	4,347
OTHER COMPREHENSIVE LOSS, NET OF TAX									(67,204)	(21,796)	(18,997)
COMPREHENSIVE INCOME ATTRIBUTABLE TO LAZARD LTD									$ 360,073	$ 138,416	$ 65,312