Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]	Class A Common Stock Held By Subsidiaries [Member]	Total Lazard Ltd Stockholders' Equity [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2017	$ 1,258,905	$ 1,298	$ 788,140	$ 1,080,413	$ (232,518)	$ (437,530)	$ 1,199,803	$ 59,102
Balance (in shares) at Dec. 31, 2017		129,766,091				10,747,142
Comprehensive income (loss):
Net income	161,661			159,692			159,692	1,969
Other comprehensive income - net of tax	13,394				13,394		13,394
Amortization of share-based incentive compensation	82,820		82,820				82,820
Dividend-equivalents	(3,767)		28,406	(32,173)			(3,767)
Class A common stock dividends	(202,384)			(202,384)			(202,384)
Purchase of Class A common stock	$ (145,949)					$ (145,949)	(145,949)
Purchase of Class A common stock (in shares)	2,662,286					2,662,286
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (benefit)	$ (107,193)		(280,020)			$ 172,827	(107,193)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (benefit) (in shares)						(4,048,104)
Business acquisitions and related equity transactions:
Delivery of Class A common stock			(61)			$ 61
Delivery of Class A common stock (in shares)						(1,858)
Class A common stock issuable (including related amortization)	145		145				145
Distributions to noncontrolling interests, net	(1,451)							(1,451)
Balance at Mar. 31, 2018	1,056,181	$ 1,298	619,430	1,005,548	(219,124)	$ (410,591)	996,561	59,620
Balance (in shares) at Mar. 31, 2018		129,766,091				9,359,466
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	96,476			97,042			97,042	(566)
Other comprehensive income - net of tax	4,961				4,960		4,960	1
Amortization of share-based incentive compensation	84,681		66,213				66,213	18,468
Dividend-equivalents	(3,050)		15,512	(17,187)			(1,675)	(1,375)
Class A common stock dividends	(103,402)			(103,402)			(103,402)
Purchase of Class A common stock	$ (192,097)					$ (192,097)	(192,097)
Purchase of Class A common stock (in shares)	5,177,948					5,177,948
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (benefit)	$ (86,776)		(296,858)			$ 210,082	(86,776)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (benefit) (in shares)						(4,906,631)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	105		105				105
Dividend-equivalents			262	(262)
Contributions from noncontrolling interests, net	381							381
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