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 (loss)
Net income	231,331			227,931			227,931	3,400
Other comprehensive income (loss) - net of tax	36,437				36,437		36,437
Amortization of share-based incentive compensation	163,001		163,001				163,001
Dividend equivalents	(4,077)		31,335	(35,412)			(4,077)
Class A common stock dividends	(242,427)			(242,427)			(242,427)
Purchase of Class A common stock	$ (184,892)					$ (184,892)	(184,892)
Purchase of Class A common stock (in shares)	4,268,479					4,268,479
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense	$ (70,900)		(209,543)			$ 138,643	(70,900)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (in shares)						(3,736,461)
Business acquisitions and related equity transactions:
Class A common stock issuable (including related amortization)	218		218				218
Distributions to noncontrolling interests, net	(1,743)							(1,743)
Other	408			204			204	204
Balance at Jun. 30, 2017	1,302,713	$ 1,298	673,242	1,166,026	(277,785)	$ (319,755)	1,243,026	59,687
Balance (in shares) at Jun. 30, 2017		129,766,091				8,160,804
Balance at Mar. 31, 2017					(296,699)
Comprehensive income (loss)
Net income	120,901
Other comprehensive income (loss) - net of tax	18,914				18,914
Balance at Jun. 30, 2017	1,302,713	$ 1,298	673,242	1,166,026	(277,785)	$ (319,755)	1,243,026	59,687
Balance (in shares) at Jun. 30, 2017		129,766,091				8,160,804
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	310,040			306,655			306,655	3,385
Other comprehensive income (loss) - net of tax	(20,982)				(20,981)		(20,981)	(1)
Amortization of share-based incentive compensation	169,830		169,830				169,830
Dividend equivalents	(4,681)		33,627	(38,308)			(4,681)
Class A common stock dividends	(255,228)			(255,228)			(255,228)
Purchase of Class A common stock	$ (223,795)					$ (223,795)	(223,795)
Purchase of Class A common stock (in shares)	4,147,526					4,147,526
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense	$ (116,730)		(340,963)			$ 224,233	(116,730)
Delivery of Class A common stock in connection with share-based incentive compensation and related tax expense (in shares)						(5,172,915)
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)	289		289				289
Dividend-equivalents			1,151	(1,151)
Distributions to noncontrolling interests, net	(4,544)							(4,544)
Balance at Jun. 30, 2018	1,113,104	$ 1,298	652,013	1,092,381	(253,499)	$ (437,031)	1,055,162	57,942
Balance (in shares) at Jun. 30, 2018		129,766,091				9,719,895
Balance at Mar. 31, 2018					(219,124)
Comprehensive income (loss)
Net income	148,379
Other comprehensive income (loss) - net of tax	(34,376)				(34,375)			(1)
Balance at Jun. 30, 2018	$ 1,113,104	$ 1,298	$ 652,013	$ 1,092,381	$ (253,499)	$ (437,031)	$ 1,055,162	$ 57,942
Balance (in shares) at Jun. 30, 2018		129,766,091				9,719,895