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]	Series A Preferred Stock [Member]
Balance at Dec. 31, 2015	$ 1,367,306	$ 1,298	$ 600,034	$ 1,123,728	$ (234,356)	$ (177,249)	$ 1,313,455	$ 53,851
Balance (in shares) at Dec. 31, 2015		129,766,091				4,253,381			7,921
Comprehensive income (loss):
Net income	264,705			259,716			259,716	4,989
Other comprehensive income (loss) - net of tax	(1,732)				(1,732)		(1,732)
Amortization of share-based incentive compensation	213,144		213,144				213,144
Dividend-equivalents	(3,080)		32,849	(35,929)			(3,080)
Class A common stock dividends	(289,326)			(289,326)			(289,326)
Purchase of Class A common stock	$ (228,865)					$ (228,865)	(228,865)
Purchase of Class A common stock (in shares)	6,656,250					6,656,250
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense/benefit	$ (48,662)		(216,610)			$ 167,948	(48,662)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense/benefit (in shares)						(4,217,819)
Business acquisitions and related equity transactions:
Delivery of Class A common stock and related tax benefit	12,653		(21,777)			$ 34,430	12,653
Delivery of Class A common stock and related tax benefit (in shares)						(913,722)
Class A common stock issuable (including related amortization)	6,313		6,313				6,313
Distributions to noncontrolling interests, net	(873)							(873)
Other	9,559		9,559				9,559
Balance at Sep. 30, 2016	1,301,142	$ 1,298	623,512	1,058,189	(236,088)	$ (203,736)	1,243,175	57,967
Balance (in shares) at Sep. 30, 2016		129,766,091				5,778,090			7,921
Balance at Jun. 30, 2016					(237,030)
Comprehensive income (loss):
Net income	112,618
Other comprehensive income (loss) - net of tax	942				942
Balance at Sep. 30, 2016	1,301,142	$ 1,298	623,512	1,058,189	(236,088)	$ (203,736)	1,243,175	57,967
Balance (in shares) at Sep. 30, 2016		129,766,091				5,778,090			7,921
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 (loss):
Net income	342,801			337,141			337,141	5,660
Other comprehensive income (loss) - net of tax	52,551				52,549		52,549	2
Amortization of share-based incentive compensation	220,648		220,648				220,648
Dividend-equivalents	(4,997)		36,482	(41,479)			(4,997)
Class A common stock dividends	(292,293)			(292,293)			(292,293)
Purchase of Class A common stock	$ (252,538)					$ (252,538)	(252,538)
Purchase of Class A common stock (in shares)	5,838,520					5,838,520
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense/benefit	$ (72,203)		(212,271)			$ 140,068	(72,203)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense/benefit (in shares)						(3,772,169)
Business acquisitions and related equity transactions:
Delivery of Class A common stock and related tax benefit	1,437		(472)			$ 1,909	1,437
Delivery of Class A common stock and related tax benefit (in shares)						(47,474)
Class A common stock issuable (including related amortization)	363		363				363
Distributions to noncontrolling interests, net	(3,059)							(3,059)
Other	408			204			204	204
Balance at Sep. 30, 2017	1,368,475	$ 1,298	732,981	1,219,303	(261,673)	$ (384,067)	1,307,842	60,633
Balance (in shares) at Sep. 30, 2017		129,766,091				9,647,663
Balance at Jun. 30, 2017					(277,785)
Comprehensive income (loss):
Net income	111,470
Other comprehensive income (loss) - net of tax	16,114				16,112
Balance at Sep. 30, 2017	$ 1,368,475	$ 1,298	$ 732,981	$ 1,219,303	$ (261,673)	$ (384,067)	$ 1,307,842	$ 60,633
Balance (in shares) at Sep. 30, 2017		129,766,091				9,647,663