Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect Period Of Adoption Adjustment [Member]	Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Common Stock [Member]	Common Stock [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Additional Paid-In-Capital [Member]	Additional Paid-In-Capital [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect Period Of Adoption Adjustment [Member]	Retained Earnings [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Class A Common Stock Held By Subsidiaries [Member]	Class A Common Stock Held By Subsidiaries [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Total Lazard Ltd Stockholders' Equity [Member]	Total Lazard Ltd Stockholders' Equity [Member] Cumulative Effect Period Of Adoption Adjustment [Member]	Total Lazard Ltd Stockholders' Equity [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member] Cumulative Effect Period Of Adoption Adjusted Balance [Member]
Balance at Dec. 31, 2018	$ 970,093			$ 1,298		$ 750,692		$ 1,195,563			$ (273,818)		$ (756,884)		$ 916,851			$ 53,242
Balance (in shares) at Dec. 31, 2018				129,766,091									17,574,805
Comprehensive income (loss):
Net income (loss)	169,989							162,819							162,819			7,170
Other comprehensive income (loss) - net of tax	1,833										1,834				1,834			(1)
Amortization of share-based incentive compensation	161,083					125,202									125,202			35,881
Dividend equivalents	(4,681)					20,142		(22,761)							(2,619)			(2,062)
Class A common stock dividends	(155,324)							(155,324)							(155,324)
Purchase of Class A common stock	$ (351,712)												$ (351,712)		(351,712)
Purchase of Class A common stock (in shares)	9,715,003												9,715,003
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit	$ (91,731)					(327,572)							$ 235,841		(91,731)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit (in shares)													(5,528,555)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	13,482					13,482									13,482
Dividend equivalents						396		(396)
Distributions to noncontrolling interests, net	(6,618)																	(6,618)
Consolidated VIEs	11,464																	11,464
Balance at Jun. 30, 2019	717,878			$ 1,298		582,342		1,179,901			(271,984)		$ (872,755)		618,802			99,076
Balance (in shares) at Jun. 30, 2019				129,766,091									21,761,253
Balance at Mar. 31, 2019	771,372			$ 1,298		535,926		1,171,754			(268,858)		$ (738,899)		701,221			70,151
Balance (in shares) at Mar. 31, 2019				129,766,091									17,846,122
Comprehensive income (loss):
Net income (loss)	73,513							65,777							65,777			7,736
Other comprehensive income (loss) - net of tax	(3,128)										(3,126)				(3,126)			(2)
Amortization of share-based incentive compensation	76,402					58,989									58,989			17,413
Dividend equivalents	(1,631)					4,630		(5,574)							(944)			(687)
Class A common stock dividends	(51,922)							(51,922)							(51,922)
Purchase of Class A common stock	(159,615)												$ (159,615)		(159,615)
Purchase of Class A common stock (in shares)													4,537,055
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit	(4,955)					(30,714)							$ 25,759		(4,955)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit (in shares)													(621,924)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	13,377					13,377									13,377
Dividend equivalents						134		(134)
Distributions to noncontrolling interests, net	(6,999)																	(6,999)
Consolidated VIEs	11,464																	11,464
Balance at Jun. 30, 2019	717,878			$ 1,298		582,342		1,179,901			(271,984)		$ (872,755)		618,802			99,076
Balance (in shares) at Jun. 30, 2019				129,766,091									21,761,253
Balance at Dec. 31, 2019	681,574	$ (7,575)	$ 673,999	$ 1,128	$ 1,128	41,020	$ 41,020	1,193,570	$ (7,575)	$ 1,185,995	(293,648)	$ (293,648)	$ (332,079)	$ (332,079)	609,991	$ (7,575)	$ 602,416	71,583	$ 71,583
Balance (in shares) at Dec. 31, 2019				112,766,091	112,766,091								8,513,493	8,513,493
Comprehensive income (loss):
Net income (loss)	131,407							137,480							137,480			(6,073)
Other comprehensive income (loss) - net of tax	(15,273)										(15,273)				(15,273)
Amortization of share-based incentive compensation	140,705					138,136									138,136			2,569
Dividend equivalents	(3,567)					11,345		(12,540)							(1,195)			(2,372)
Class A common stock dividends	(97,892)							(97,892)							(97,892)
Purchase of Class A common stock	$ (95,227)												$ (95,227)		(95,227)
Purchase of Class A common stock (in shares)	2,912,035
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit	$ (70,069)					(138,556)		(74,228)					$ 142,715		(70,069)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit (in shares)													(3,619,213)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	104					104									104
Delivery of Class A common stock						(692)							$ 692
Delivery of Class A common stock (in shares)													(21,212)
Dividend equivalents						917		(917)
Distributions to noncontrolling interests, net	(1,794)																	(1,794)
Consolidated VIEs	19,458																	19,458
Other	2,117							2,117							2,117
Balance at Jun. 30, 2020	683,968			$ 1,128		52,274		1,140,015			(308,921)		$ (283,899)		600,597			83,371
Balance (in shares) at Jun. 30, 2020				112,766,091									7,785,103
Balance at Mar. 31, 2020	559,617			$ 1,128				1,119,176			(333,412)		$ (300,459)		486,433			73,184
Balance (in shares) at Mar. 31, 2020				112,766,091									8,235,358
Comprehensive income (loss):
Net income (loss)	73,076							73,458							73,458			(382)
Other comprehensive income (loss) - net of tax	24,490										24,491				24,491			(1)
Amortization of share-based incentive compensation	68,544					67,386									67,386			1,158
Dividend equivalents	(1,704)					4,628		(5,146)							(518)			(1,186)
Class A common stock dividends	(49,133)							(49,133)							(49,133)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit	(3,689)					(20,230)							$ 16,541		(3,689)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax benefit (in shares)													(449,667)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	52					52									52
Delivery of Class A common stock						(19)							$ 19
Delivery of Class A common stock (in shares)													(588)
Dividend equivalents						457		(457)
Distributions to noncontrolling interests, net	(408)																	(408)
Consolidated VIEs	11,006																	11,006
Other	2,117							2,117							2,117
Balance at Jun. 30, 2020	$ 683,968			$ 1,128		$ 52,274		$ 1,140,015			$ (308,921)		$ (283,899)		$ 600,597			$ 83,371
Balance (in shares) at Jun. 30, 2020				112,766,091									7,785,103