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, 2016	$ 1,293,813	$ 1,298	$ 688,231	$ 1,134,186	$ (314,222)	$ (273,506)	$ 1,235,987	$ 57,826
Balance (in shares) at Dec. 31, 2016		129,766,091				7,628,786
Adjustment for the cumulative effect on prior years from the adoption of new accounting guidance related to share-based incentive compensation at Dec. 31, 2016	81,544			81,544			81,544
Balance, as adjusted at Dec. 31, 2016	1,375,357	$ 1,298	688,231	1,215,730	(314,222)	$ (273,506)	1,317,531	57,826
Comprehensive income:
Net income	110,430			107,553			107,553	2,877
Other comprehensive income - net of tax	17,523				17,523		17,523
Amortization of share-based incentive compensation	77,527		77,527				77,527
Dividend-equivalents	(3,054)		25,977	(29,031)			(3,054)
Class A common stock dividends	(192,264)			(192,264)			(192,264)
Purchase of Class A common stock	$ (106,048)					$ (106,048)	(106,048)
Purchase of Class A common stock (in shares)	2,464,967					2,464,967
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense	$ (65,765)		(183,736)			$ 117,971	(65,765)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (in shares)						(3,214,282)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	74		74				74
Distributions to noncontrolling interests, net	(1,001)							(1,001)
Other	408							408
Balance at Mar. 31, 2017	1,213,187	$ 1,298	608,073	1,101,988	(296,699)	$ (261,583)	1,153,077	60,110
Balance (in shares) at Mar. 31, 2017		129,766,091				6,879,471
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:
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	$ (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 (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